Effect of substrate on graphene-based interconnects

Layered insulator hexagonal boron nitride (h-BN) has been used as a substrate for graphene interconnects. Three different material systems, i.e. CVD graphene on h-BN, CVD graphene on SiO₂, and exfoliated graphene on SiO₂ have been studied in terms of resistivity, carrier mobility, and breakdown power density. A remarkable reduction is observed in resistivity of CVD graphene interconnects on h-BN substrate as compared to CVD graphene on SiO₂ and exfoliated graphene on SiO₂ (reduced by 19 times and 8 times respectively). The carrier mobility shows good improvement with CVD graphene on h-BN showing a mobility of ~15,000 cm²/V-s at electric field strength of 0.5 MV/cm. High thermal conductivity of h-BN as compared to SiO₂ facilitates heat dissipation and leads to improvement in breakdown power. Current annealing does not appreciably shift the Dirac Point on h-BN which may result from the interface-state-free nature of h-BN substrate. High voltage annealing is required to cleanup the channel. Switching polarity during annealing further reduces the contact resistance. Overall, it is evident that h-BN as a substrate can help resolve reliability issues and push the performance limits imposed by SiO₂ substrate on graphene-based interconnects.