which can further degrade the interconnect performance. Hence, the increase in resistivity due to scaling is further aggravated by rough surfaces of Cu interconnect. [5,6] As a result of the issues faced by conventional Cu interconnects, researchers are on a quest to find a suitable candidate for very large scale integration (VLSI) on-chip interconnects. Cu-based materials like Cu-carbon nanotube (Cu-CNT) composite, [7] Cu-Graphene hybrid, [8] and Cu-Carbon hybrid [9] have been proposed as possible substitutes for Cu interconnects. Although, it is worth noting that the related fabrication of Cubased materials faces many challenges like achieving uniform CNT-Cu distribution, compatibility with complementary metal oxide semiconductor (CMOS) technology, and lack of a fully developed fabrication process. [7][8][9] In recent years, 1D carbonbased nanomaterials like CNTs and graphene nanoribbons (GNRs) are of significant interest in various applications like electronic devices, VLSI on-chip interconnects, through silicon via (TSVs) for 3D ICs, sensors, optics, medicine, mechanics, spintronics and energy storage devices, owing to their exceptional electronic, optical, thermal, and mechanical properties. [10][11][12] Moreover, both GNRs and CNTs show higher current densities, electrical and thermal conductivities than Cu. [13] Hence, researchers proposed GNRs and CNTs as emerging alternatives to conventional Cu for VLSI on-chip interconnects. [13][14][15][16] GNRs having planar structures are more consistent with the semiconductor industry's fabrication technology, [17,18] making GNRs preferable to CNTs.GNRs are classified into single-layer (SLGNR) and multilayer (MLGNR) GNR, where SLGNR with a single layer of GNR has very high intrinsic resistance. Hence, to achieve lower resistance and better performance, MLGNR is proposed in which multiple GNR layers are stacked on top of one another. [19,20] The MLGNRs can be further classified based on the contact formed between metal and MLGNR, i.e., top-contact (TC-MLGNR) and side-contact (SC-MLGNR) MLGNR. SC-MLGNR has lower resistance as all the layers are physically coupled to metal contacts, whereas only the topmost layer forms a connection with the metal contact in TC-MLGNR, leading to its inferior performance. However, in the present scenario, fabrication of TC-MLGNR is less challenging and practically feasible than SC-MLGNR. [19,20] TC-MLGNRs
Scattering source‐based mean free path (MFP) and circuit modeling are proposed for three different configurations of undoped multilayer graphene nanoribbon (U‐MLGNR) (viz. horizontal top‐contact (HTC), horizontal side‐contact (HSC), and vertical top‐contact (VTC)). A similar analysis is carried out for doped HTC‐MLGNR (D‐HTC‐MLGNR) considering dopants viz. Li, FeCl3, and AsF5, for a temperature range of 300–500 K. The optimistic intrinsic‐phonon limited (Λeff,1(T)) and realistic scattering limited (Λeff,2(T)) effective MFP models are considered to derive the equivalent resistance of MLGNR. The performance of MLGNR variants, considering Λeff,1(T) and Λeff,2(T), is compared to copper (Cu) (with smooth and rough surface) in terms of coupled line crosstalk‐induced delay (XT‐D). The results show that the MLGNR variants outperform Cu interconnects in terms of XT‐D, for Λeff,1(T). However, structural edge roughness being the dominant scattering source in Λeff,2(T), severely degrades the performance of MLGNR variants in comparison to Cu counterparts. Moreover, for Λeff,1(T) and Λeff,2(T), Li‐D HTC‐MLGNR outperforms other MLGNR variants. Also, among the MLGNR variants, U‐VTC‐MLGNR exhibits a minimum average relative penalty of 21.58 × 102% in terms of XT‐D, when Λeff,2(T) is considered as against Λeff,1(T). Li‐D HTC‐MLGNR with optimized width exhibits 10.59× lower XT‐D and 8.85× higher XT‐D for Λeff,1(T) and Λeff,2(T), respectively, compared to smooth Cu. The optimized Li‐D HTC‐MLGNR demonstrates a reduction of 85.48% and 74.67% in XT‐D values for Λeff,1 (T) and Λeff,2 (T), respectively, when compared to mixed carbon nanotube (MCNT) bundle interconnects.
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