Electrical Resistivity Evolution of Electrodeposited Ruthenium- and Molybdenum-based Nanowires for Interconnect Application

It is challenging to achieve historically anticipated improvements in the performance of integrated circuits (ICs) because the cost and complexity of the associated technology increase with each generation. As downscaling accelerates, the electrical resistance and diffusion to low-k dielectrics of conventional Cu/Ta/TaN interconnect become a major problem [1]. The reduction in the cross-sectional area of the interconnect causes an increase in the resistance of the interconnection structure, which causes RC delay and energy consumption. A liner/barrier whose thickness cannot be reduced any further drastically reduces the volume of the conductor in the trench structure, accelerating RC delay and making the process difficult [2]. Consequently, the demand for advanced interconnect metallization has increased. Therefore, the microelectronics industry is searching for new materials and processes [3].<br/>This study investigates the electrical properties and microstructural evolution of nanoscale Ruthenium (Ru) and Molybdenum (Mo)-based metallic nanowires prepared via template-assisted electrodeposition. Most previous studies on advanced interconnect materials were carried out based on thin films. However, the actual structure and scale of interconnects, including vias and trenches, are nanowires with a high aspect ratio; thus, they exhibit properties significantly different from those of thin films owing to the confinement of low-dimensional systems.<br/>In addition to material properties, nanopore engineering is required to fill the confined pores at the nanoscale with metallic materials. We provide an electrochemical strategy for synthesizing Ru- and Mo-based nanowires in nanopores and characterize the effects of microstructure and phase differences on the electrical properties of nanowires in situ. We find that the electrical resistivity was affected by the composition and microstructural changes, such as the diameter of nanowires, crystallite size, and phase. Properly designed alloys of advanced interconnect materials (e.g., Co, Ru, and Mo) show superior characteristics to existing materials in various characteristics that interconnect will have. We investigate the degree of thermal diffusion into a low-dielectric material by imitating a structure similar to an actual interconnect structure. First-principles calculations show that a corresponding liner/barrier is required as a new central conductor emerges.<br/> <br/><b>Reference</b><br/>[1] D. Gall<i>, J. Appl. Phys</i>, 127, 050901 (2020)<br/>[2] C. Lo <i>et al., J. Appl. Phys</i>, 128, 080903 (2020)<br/>[3] J. H. Moon <i>et al., J. Mater. Sci. Technol.</i>, 105, 17 (2022)