This study presents the analysis and reduction of vertical crosstalk in mixed-signal 3-D integrated circuits (3-D ICs) with multilayer graphene nanoribbon (MLGNR) and multiwall carbon nanotube (MWCNT) interconnects. The 14-nm technology node is considered for both digital and analog tiers. The assessments are conducted regarding the scattering parameters (S-parameters) for the equivalent circuit model of the transmission lines using the Advanced Design System (ADS) tool. Our studies demonstrate that the MLGNR transmission lines lead to lower mismatch, insertion loss, and vertical crosstalk than their MWCNT counterparts. The results show that using MLGNR improves the area overhead by more than 67% for analog and digital wires. Moreover, our model shows that the vertical noise between the analog and digital tiers is reduced by 1 and 1.62 dB when the intermediate substrate thickness increases from 20 to 30 and 40 μm. The results demonstrate that the perpendicular routing of the MLGNR interconnects reduces the vertical noise by 6.1 dB. Moreover, a 9.21-dB reduction in the vertical coupling is achieved using vertical MLGNRs in the analog IC. Our results also show that using graphene as a shield between the analog and digital chips significantly suppresses the vertical noise between the tiers, and it becomes more effective by increasing the number of graphene layers. According to our results, using one-, two-, and three-layer graphene-shield layers reduces the vertical crosstalk by 10.1, 14.9, and 19.2 dB, respectively. Moreover, the HSPICE simulations demonstrate that the MLGNR interconnects have a lower delay, power, and energy consumption than their MWCNT counterparts in the 3-D mixed-signal architecture.
