Scalable graphite/copper bishell composite for high-performance interconnects

We present the fabrication and characterizations of novel electrical interconnect test lines made of a Cu/graphite bishell composite with the graphite cap layer grown by electron cyclotron resonance chemical vapor deposition. Through this technique, conformal multilayer graphene can be formed on the predeposited Cu interconnects under CMOS-friendly conditions. The low-temperature (400 C) deposition also renders the process unlimitedly scalable. The graphite layer can boost the current-carrying capacity of the composite structure to 10⁸ A/cm², more than an order of magnitude higher than that of bare metal lines, and reduces resistivity of fine test lines by ∼10%. Raman measurements reveal that physical breakdown occurs at ∼680-720 C. Modeling the current vs voltage curves up to breakdown shows that the maximum current density of the composites is limited by self-heating of the graphite, suggesting the strong roles of phonon scattering at high fields and highlighting the significance of a metal counterpart for enhanced thermal dissipation.