Challenges and Innovations in Advanced Interconnect Metallization

As the dimensional scaling of semiconductor devices continues to accelerate, the parasitic resistance-capacitance delay in integrated circuits has become a critical factor determining overall device performance. The increasing aspect ratio and shrinking cross-sectional area of interconnects with continued chip scaling result in a rapid rise in line resistance, while the reduced spacing between lines leads to higher capacitance. These coupled effects degrade both signal transmission and energy efficiency. Despite remarkable advancements over the past three decades, the conventional Cu interconnect technology is now facing fundamental limitations due to size-dependent resistivity increases and poor compatibility with emerging low-k dielectric materials. Consequently, the development and integration of alternative interconnect materials with appropriate dielectric materials have become essential to sustain performance scaling. Alternative materials – such as ruthenium, molybdenum, and various alloy systems – are being extensively investigated owing to superior electromigration resistance and low electron scattering at the nanoscale dimensions. The semiconductor industry now stands at a critical point where innovative process technologies and integration schemes must be explored to enable the successfulimplementation of these new materials in advanced interconnects. This discussion first examines the limiting factor of conventional interconnect, and demonstrates not only the current states of Ru and Mo process as leading candidates of next generation interconnect but integration and patterning problems. Additionally, it presents the direction of interconnect process development by investigating the potential of other alternative metals.