Intercalation Doped Multilayer-Graphene-Nanoribbons for Next-Generation Interconnects

Abstract

Copper-based interconnects employed in a wide range of integrated circuit (IC) products are fast approaching a dead-end due to their increasing resistivity and diminishing current carrying capacity with scaling, which severely degrades both performance and reliability. Here we demonstrate chemical vapor deposition-synthesized and intercalation-doped multilayer-graphene-nanoribbons (ML-GNRs) with better performance (more than 20% improvement in estimated delay per unit length), 25%/72% energy efficiency improvement at local/global level, and superior reliability w.r.t. Cu for the first time, for dimensions (down to 20 nm width and thickness of 12 nm) suitable for IC interconnects. This is achieved through a combination of GNR interconnect design optimization, high-quality ML-GNR synthesis with precisely controlled number of layers, and effective FeCl intercalation doping. We also demonstrate that our intercalation doping is stable at room temperature and that the doped ML-GNRs exhibit a unique width-dependent doping effect due to increasingly efficient FeCl diffusion in scaled ML-GNRs, thereby indicating that our doped ML-GNRs will outperform Cu even for sub-20 nm widths. Finally, reliability assessment conducted under accelerated stress conditions (temperature and current density) established that highly scaled intercalated ML-GNRs can carry over 2 × 10 A/cm of current densities, whereas Cu interconnects suffer from immediate breakdown under the same stress conditions and thereby addresses the key criterion of current carrying capacity necessary for an alternative interconnect material. Our comprehensive demonstration of highly reliable intercalation-doped ML-GNRs paves the way for graphene as the next-generation interconnect material for a variety of semiconductor technologies and applications.

On-chip intercalated-graphene inductors for next-generation radio frequency electronics

“…Such high-performance and area-efficient spiral intercalated MLG inductors inherently provide the scalability, design flexibility and discreetness required for the next-generation RF-ICs and RF-ID technology needed to realize the potential of the IoT. Moreover, intercalated MLG has been recently demonstrated to address the fundamental current-carrying capacity problem of scaled copper interconnects used in IC applications 18 . Hence, our demonstration of intercalated MLG inductors could provide an 'all-carbon' back-end-of-line (BEOL) conductor technology for next-generation ICs to provide the ultimate performance and reliability in the smallest form factor possible.…”

“…Several candidates as intercalation guests (dopants) have been identified that can improve the conductivity of MLG, such as alkali metals (for example, Li, Na and K), halogens (for example, Cl 2 , Br 2 and ICl) and halides (for example, BF 3 , AsF 5 , AuCl 3 and FeCl 3 ) [18][19][20][21][22] . Among those options, bromine intercalation is favourable due to its low processing temperature, short processing time and deeper diffusion into the intercalation host (MLG), as well as the closer lattice matching of the bromine intercalation layer with that of MLG 19 .…”

“…However, further improvement in both L and Q is expected if stage-1 intercalation can be achieved (see Supplementary Section 5). There are also other intercalation guests that can induce higher and/or more stable doping than that of bromine 18,19 (see Supplementary Sections 12 and 13 for further discussions). Moreover, the Q-factors can be further increased by improvement of the contact quality 17 .…”

Downscaling inductors with graphene

“…In low-dimensional carbon allotropes, the kinetic inductance can potentially be significantly larger than in conventional metals, due to their larger momentum relaxation times and small number of conducting channels 2,3 . Notably, Banerjee and colleagues show that an analytical estimation of the kinetic inductance of intercalated multilayer graphene exhibits a ∕ n 1 2D dependence, compared with a ∕n 1 2D dependency for multilayer graphene without intercalation, where n 2D represents the areal carrier density.…”

“…The researchers also indicated that an increase in the number of layers in the multilayer graphene leads to a decrease in the kinetic inductance, but an appropriate number of layers in the multilayer graphene is necessary to lower the contact resistance. Previous work has indicated that higher bromine concentrations 4 , or other intercalation guests 3,5 , can lead to increased conductivity in graphene, which suggests that further down-scaling of the size of the intercalated graphene inductors could also be possible.…”