Electrical and thermal characterization of carbon nanofibers for interconnect and packaging applications

Copper interconnect technology is rapidly approaching its scaling limit due to a variety of factors involved with reducing feature size including: increasing resistivity, reliability concerns due to electromigration, and excessive power dissipation related to ever-increasing clock frequencies. The aim of this work is to present a series of fundamental electrical and thermal measurements and models to demonstrate the viability of implementing carbon nanofiber (CNF) structures into next-generation integrated circuit technologies. Through the use of various characterization techniques, the structural, electrical, and thermal properties of CNFs are revealed, and show great potential for carbon-based nanostructures in integrated circuit applications.; The temperature-dependent electrical characteristics of vertically aligned CNF arrays for on-chip interconnect applications are presented. The electrical application of CNFs for on-chip interconnects is explored in three parts. First, the electron transport mechanisms in these structures are investigated using I-V measurements over a broad temperature range (4K-300K). The measured resistivity of CNF arrays is modeled based on known two-dimensional electron conduction mechanism in a disordered medium. The model assumptions are verified using high-resolution scanning transmission electron microscopy (STEM) of the CNF-metal interface. Second, based on the developed low-temperature CNF conduction model, the ideal material for efficient electron transport is found to be a-axis graphite, exhibiting a morphology closely resembling multi-wall carbon nanotubes. To this end, palladium was used as a catalyst material for the plasma-enhanced chemical vapor deposition (PECVD) of CNFs as an alternative to nickel to improve the graphtic structure of the CNF. Finally, electrical reliability measurements are performed at different temperatures to demonstrate the robust nature and high current carrying capability of CNFs for interconnect applications.; Thermal properties of CNFs are investigated using a novel copper (Cu)-embedded CNF array for thermal management applications. Fabrication of the composite material is based on techniques derived from high-aspect ratio copper filling. A copper electrochemical deposition (ECD) recipe is developed for optimal gap filling between the CNFs in the array. Two types of thermal resistance characterization are performed on the CNF-Cu composite: (1) An ASTM D-5470 based characterization technique and (2) A photothermal analysis technique. Both results agree well and demonstrate the high thermal conductance of the CNF-Cu composite for thermal interface material applications.; A variety of modeling techniques are employed to investigate temperature-dependent characteristics of CNFs. Low-temperature modeling is performed to investigate the conductivity limit of CNFs and to elucidate the physics of electron conduction within the material. Electrothermal effects are modeled using tunneling theory to describe electron transport across electrode-CNF interfaces, and the effects of contact annealing. Since self-heating effects are pivotal in one-dimensional conductors and interconnects, electrothermal modeling is of absolute necessity to describe Joule heating-induced breakdown in the CNF. The modeling work performed here enhances our understanding of the coupled effects between electrical and thermal transport in CNFs.