Electrical And Thermal Behavior In Nanoscale Copper Interconnect Systems

The increase of Cu interconnect resistivity with shrinking wire cross section, a phenomenon referred to as " size effect", impacts the time delay and thus represents a major challenge for modern integrated circuits (ICs) technology. There is a clear need that calls for more accurate quantitative methods to directly calculate the resistivity arising from various scattering mechanisms. On the other hand, this increasing Cu resistivity in addition to continually enhanced current densities results in higher self-heating of interconnects. Moreover, low-k dielectrics with inherently lower thermal conductivity make heat conduction from interconnect layers to the heat sink difficult. Therefore, the thermal assessment of interconnects system as a sum of accurate thermal information respectively from their constituting layers is becoming essential for thermal management and optimal design of ICs.In this dissertation, surface phonon dispersion and corresponding scattering probability are calculated using first-principles technique based on density functional perturbation theory (DFPT). Deviating from the bulk modes, the surface phonon dispersion exhibits a number of "optical" phonon braches due to the symmetry-breaking at the surface. The transition probability of electron during surface inelastic scattering is evaluated based on spectral Eliashberg function, showing three main peaks at 2.5,5.5 and 6.8 Thz and as a result, indicating an effective energy-loss channel of electrons through its interaction with surface phonons. Surface phonon scattering combined with other scattering mechanisms mentioned above has been numerically studied in this dissertation using Monte Carlo method as a statistical solution to Boltzmann transport equation. Besides, a coupled thermal-electrical estimation within the Monte Carlo simulation is performed via calculating temperature rise due to phonon emission during surface inelastic interaction.We also have conducted fundamental studies for thermal transport both in nanoscale and porous solids. Instead of using a phenomenological macroscale model, e.g., Fourier law of heat conduction, microscale simulations of energy transport are performed using the lattice Boltzmann method (LBM) applied to phonon transport, successfully capturing the transient sub-continuum thermal behavior, such as ballistic thermal transport, hotspot generation and temperature slip. In addition, for the porous material, anomalously large pores, so called "killer pores", are modeled in the framework of LBM. As demonstrated by simulation, the existence of killer pores will exacerbate the inhomogeneity of temperature gradient, especially in the region close to the boundary. As an accurate technique for measuring the thermal conductivity of thin films,3?method is enabling new capabilities for nanoscale thermal metrology. It has been found in the low-frequency regime, the experimentally determined thermal conductivity of thin dielectric films deviates significantly from the theoretical expectation, which makes Cahill 3 w thermal model fail in this range. The main mechanism responsible for this deviation is, to date, still controversial. A generalized thermal model is then proposed aiming to characterize two-dimensional thermal transport and illustrate the main mechanism of the deviating behavior. The frequency-dependent thermal response of test samples in 3 w measurements is further investigated by performing a coupled thermo-electrical transient analysis. Additionally, the inherent correlation between critical failure frequency of Cahill model and heater strip structure is revealed based on the " standing heat wave " model, which can be used as one guideline for the design of the heater strip structure. In the end, our investigation also highlights the possibility of extraction of thermal conductivity of the metallic strip using the proposed 3?thermal model.The theoretical and experimental results made in this research provide physical insight for understanding and characterizing electrical and thermal characteristic of Cu interconnect system in nano scale. At the same time, the present work also provides elementary basis for the development of the coupled thermal-electrical- mechanical interconnect model in the future.