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 similar to 15,000 cm(2)/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 clean-up 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.