The main objective of this thesis is to design reliable clock-distribution networks and power-delivery networks for three-dimensional integrated circuits (3D ICs) using through-silicon vias (TSVs). This dissertation supports this goal by addressing six research topics. The first four works focus on 3D clock tree synthesis for low power, pre-bond testability, TSV-induced obstacle avoidance, and TSV utilization. The last two works develop modeling approaches for reliability analysis on 3D power-delivery networks. In the first work, a clock synthesis algorithm is developed for low-power and low-slew 3D clock network design. The impact of various design parameters on clock performance, including the wirelength, clock power, clock slew, and skew, is investigated. These parameters cover the TSV count, TSV parasitics, the maximum loading capacitance of the clock buffers, and the supply voltage. In the second work, a clock synthesis algorithm is developed to construct 3D clock networks for both pre-bond testability and post-bond operability. Pre-bond testing of 3D stacked ICs involves testing each individual die before bonding, which can improve the overall yield of 3D ICs by avoiding stacking defective dies with good ones. Two key techniques including TSV-buffer insertion and redundant tree generation are implemented to minimize clock skew and ensure pre-bond testing. The impact of TSV utilization and TSV parasitics on clock power is also investigated. In the third work, an obstacle-aware clock tree synthesis method is presented for through-silicon-via (TSV)-based 3D ICs. A unique aspect of this problem lies in the fact that various types of TSVs become obstacles during 3D clock routing including signal, power/ground, and clock TSVs. These TSVs may occupy silicon area or routing layers. The generated clock tree does not sacrifice wirelength or clock power too much and avoids TSV-induced obstacles. In the fourth work, a decision-tree-based clock synthesis (DTCS) method is developed for low-power 3D clock network design, where TSVs form a regular 2D array. This TSV array style is shown to be more manufacturable and practical than layouts with TSVs located at irregular spots. The DTCS method explores the entire solution space for the best TSV array utilization in terms of low power. Close-to-optimal solutions can be found for power efficiency with skew minimization in short runtime. In the fifth work, current crowding and its impact on 3D power grid integrity is investigated. Due to the geometry of TSVs and connections to the global power grid, significant current crowding can occur. The current density distribution within a TSV and its connections to the global power grid is explored. A simple TSV model is implemented to obtain current density distributions within a TSV and its local environment. This model is checked for accuracy by comparing with identical models simulated using finite element modeling methods. The simple TSV models are integrated with the global power wires for detailed chip-scale power analysis. In the sixth work, a comprehensive multi-physics modeling approach is developed to analyze electromigration (EM) in TSV-based 3D connections. Since a TSV has regions of high current density, grain boundaries play a significant role in EM dominating atomic transport. The transient analysis is performed on atomic transport including grain and grain boundary structures. The evolution of atomic depletion and accumulation is simulated due to current crowding. And the TSV resistance change is modeled.

L'application d'un champ de forces externes à un milieu liquide contenant un ou plusieurs solutés permet d'agir sur sa composition en modifiant les conditions d'équilibre thermodynamique. En particulier surimposer un champ électrique aux transferts entre phases non miscibles conduit à rendre complètes l'extraction liquide liquide d'un soluté contenu dans une phase non polaire ou la dissolution d'un sel réputé insoluble. Le passage d'un courant électrique continu d'intensité. constante dans une solution électrolytique diluée, initialement homogène et au repos dans des conditions isothermes, provoque la migration des ions vers l'une et l'autre électrode. Il en résulte des variations locales de concentration qui modifient 1a composition de la solution. On s'intéresse plus particulièrement aux phénomènes qui apparaissent lorsqu'on applique le courant à une solution aqueuse d'acides (ou de bases) contenue dans un tube en U, éventuellement au contact au niveau de la cathode (ou de l'anode) avec une phase organique, non miscible et non conductrice, mais contenant un électrolyte présent dans l'eau. Par extension on étudie aussi les phénomènes qui accompagnent le passage d'un courant électrique dans un milieu liquide contenant un sel quasiment insoluble. L'évolution dans le temps du système s'explique à partir des lois générales gouvernant les phénomènes mis en jeu qui sont l'électromigration, la diffusion et les trarssferts interfaciaux. Ayant défi'1i les conditions initiales, on établit l'expression des flux de matière associés à ces phénomènes, puis, tenant compte des équilibres électrochimiques, on en déduit, par simple bilan, les équations donnant les variations sur les concentrations locales de chaque espèce. La résolution de ce système complexe d'équations aux dérivées partielles est réalisée sur ordinateur à l'aide d'une méthode pas à pas, généralisable à un mélange quelconque de solutés. On obtient ainsi le profil de concentration de chaque espèce le long de l'axe du tube, à tout instant.

Ce travail est une étude expérimentale permettant de mettre en évidence la cartographie générale de l’ensemble des états d’écoulement obtenus entre le régime laminaire de Couette et la turbulence. L’ensemble des expériences a été réalisé dans un dispositif appelé système Taylor-Couette (STC), composé de deux cylindres concentriques avec le cylindre intérieur tournant. Ces différentes instabilités (SPI, TVF, WVF, MWVF, TTVF), qui dépendent principalement du nombre de Taylor (Ta), seront obtenues avec ou sans débit axial dans le STC selon des protocoles d’analyse bien définis et nous notons que le nombre de Reynolds axial (Reax) a un effet de stabilisation de l’écoulement. Les vortex de Taylor toroïdaux, ondulés ou ondulés modulés, ont été caractérisés en termes de gradient pariétal de vitesse, de nombre d’ondes, de longueur d’ondes axiales et azimutales, de la vitesse de déplacement axial, de fréquence et de la vitesse de révolution ; la polarographie sera utilisée comme technique de mesure. La vitesse du cylindre intérieur (Ta) est essentiellement le seul phénomène agissant sur l’évolution de ces paramètres. L’utilisation de la sonde tri-segmentée dans la caractérisation des structures tourbillonnaires a contribué à la compréhension des mécanismes d’interaction vortex-paroi et à la détermination des composantes azimutale et axiale du gradient pariétal de vitesse. / This work is an experimental study to highlight general mapping of the set of states obtained from the Couette laminar flow to turbulence. All experiments were performed in a device called Taylor-Couette system (TCS) which consists of two concentric cylinders with the inner cylinder rotating. The flow regimes (SPI, TVF, WVF, MWVF, TTVF), which depend mainly on the Taylor number (Ta), were obtained with or without axial flow in the TCS according to well-defined experimental protocols. We noted that the axial Reynolds number (Reax) has astabilizing effect on the flow. Using electrodiffusion method and analysis of films, the toroidal Taylor vortices, wavy or wavy modulated flow, were characterized in terms of the wall velocity gradients, wave number, axial and azimuthal wavelength, the axial velocity of vortex displacement, and there frequencies. The Taylor number has substantial effect on the evolution of these parameters in the investigated range. The use of three-segment electrodiffusion has contributed to the understanding of the mechanisms of vortex-wall interaction and the determination of the azimuthal and axial components of the wall velocity gradient.

Extracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron-microelectrode cleft. This has made it difficult to correlate the extracellularly recorded signals with the intracellular signals recorded using conventional patch-clamp electrophysiology. For bringing about an improvement in the signalto-noise ratio of the signals recorded on the extracellular microelectrodes and to explore strategies for engineering the neuron-electrode interface there exists a need to model, simulate and characterize the cell-sensor interface to better understand the mechanism of signal transduction across the interface. Efforts to date for modeling the neuron-electrode interface have primarily focused on the use of point or area contact linear equivalent circuit models for a description of the interface with an assumption of passive linearity for the dynamics of the interfacial medium in the cell-electrode cleft. In this dissertation, results are presented from a nonlinear dynamic characterization of the neuroelectronic junction based on Volterra-Wiener modeling which showed that the process of signal transduction at the interface may have nonlinear contributions from the interfacial medium. An optimization based study of linear equivalent circuit models for representing signals recorded at the neuron-electrode interface subsequently iv proved conclusively that the process of signal transduction across the interface is indeed nonlinear. Following this a theoretical framework for the extraction of the complex nonlinear material parameters of the interfacial medium like the dielectric permittivity, conductivity and diffusivity tensors based on dynamic nonlinear Volterra-Wiener modeling was developed. Within this framework, the use of Gaussian bandlimited white noise for nonlinear impedance spectroscopy was shown to offer considerable advantages over the use of sinusoidal inputs for nonlinear harmonic analysis currently employed in impedance characterization of nonlinear electrochemical systems. Signal transduction at the neuron-microelectrode interface is mediated by the interfacial medium confined to a thin cleft with thickness on the scale of 20-110 nm giving rise to Knudsen numbers (ratio of mean free path to characteristic system length) in the range of 0.015 and 0.003 for ionic electrodiffusion. At these Knudsen numbers, the continuum assumptions made in the use of Poisson-Nernst-Planck system of equations for modeling ionic electrodiffusion are not valid. Therefore, a lattice Boltzmann method (LBM) based multiphysics solver suitable for modeling ionic electrodiffusion at the mesoscale neuron-microelectrode interface was developed. Additionally, a molecular speed dependent relaxation time was proposed for use in the lattice Boltzmann equation. Such a relaxation time holds promise for enhancing the numerical stability of lattice Boltzmann algorithms as it helped recover a physically correct description of microscopic phenomena related to particle collisions governed by their local density on the lattice. Next, using this multiphysics solver simulations were carried out for the charge relaxation dynamics of an electrolytic nanocapacitor with the intention of ultimately employing it for a simulation of the capacitive coupling between the neuron and the v planar microelectrode on a microelectrode array (MEA). Simulations of the charge relaxation dynamics for a step potential applied at t = 0 to the capacitor electrodes were carried out for varying conditions of electric double layer (EDL) overlap, solvent viscosity, electrode spacing and ratio of cation to anion diffusivity. For a large EDL overlap, an anomalous plasma-like collective behavior of oscillating ions at a frequency much lower than the plasma frequency of the electrolyte was observed and as such it appears to be purely an effect of nanoscale confinement. Results from these simulations are then discussed in the context of the dynamics of the interfacial medium in the neuron-microelectrode cleft. In conclusion, a synergistic approach to engineering the neuron-microelectrode interface is outlined through a use of the nonlinear dynamic modeling, simulation and characterization tools developed as part of this dissertation research.