Correlating The Chemistry and Process With The Impurity, Structure and Properties of Electrodeposited Cobalt for Advanced Interconnects

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The network of metal wires in semiconductor chips are referred to as interconnects. These wires connect the transistors and carry the electronic signals for different functions of the circuitry. The resistivity of copper in state-of-the-art interconnects exponentially increases as the dimensions of semiconductor devices decrease. Cobalt has emerged as a top candidate among alternative materials to replace copper, and it will allow further advancement of semiconductor technology. However, the chemistry and processes that are needed for fabricating cobalt interconnects are still being developed, and there is insufficient information about how the chemistry and processing impact the structure and properties of such interconnects. This award will provide the fundamental research to fill this knowledge gap. The research will focus on how organic additives used in electrodeposition enable the fabrication of cobalt interconnects and control the incorporation of impurities in cobalt. More importantly, cobalt will be used as an example to provide a general understanding of how different impurity elements in electrodeposited metals impact the microstructures and electrical properties of the metal. The latter are important metrics for applications in advanced device fabrication. The research will be used to showcase student research activities in a new Electrochemical Society student chapter. In addition, a new class module on electrodeposition and microfabrication will be developed for an undergraduate level electrochemical engineering course.The synergistic interactions between multi-component organic additives that have been used in copper interconnect fabrication requires a long incubation time and faces challenges for interconnect structures with dimension below 30 nm. On the other hand, a newly discovered molecule, dioxime, results in an agitation-dependent strong suppression on cobalt deposition. It enables the preferential growth of cobalt at the bottom of the structure, where the electrolyte is stagnant, due to the lack of agitation. This project employs various derivatives of dioxime molecules to dissect the mechanisms of such suppression effects and how different impurities become incorporated into the deposited metals. Furthermore, local electrode atom probe will be used in conjunction with electron microscopy techniques and in-situ electrical measurements to understand the distribution of different impurity elements as well as their impacts on the microstructure evolution and resistivity change of cobalt. Template electrodeposited cobalt nanowires will be used to characterize electromigration of small lines without the use of advanced lithography techniques.