Topological Metal MoP Nanowire for Interconnect

Abstract

of interconnects due to its ever-increasing resistivity that stems from surface and grain boundary electron scattering. [3] The high resistivity of current Cu interconnects can account for up to 35% of total signal delays and nearly half of dynamic power dissipation in computer chips. [4] Thus, future energy-efficient computing technologies require breakthroughs in interconnect technologies, [5] particularly in new interconnect materials.Topological semimetals are promising materials for low resistance interconnects as their topologically protected surface electrons are forbidden to backscatter. [6][7][8] Several experimental studies on nanostructured topological semimetals show promising results. The Weyl semimetal NbAs, for example, exhibit a factor of ten decrease in resistivity from bulk crystals (35 µΩ cm) to nanobelts (≈3 µΩ cm) at room temperature. [9] Similarly, recent theoretical results from IBM predict that the multifold fermion system CoSi would exhibit lower resistivity than Cu at very small dimensions as the current conduction is dominated by Fermi-arc surface states. [10] Among recently reported topological metals, molybdenum phosphide (MoP) is a simple binary compound that was predicted [11] and experimentally confirmed to host topologically protected fermions. [12] Single crystal MoP shows extremely low resistivity and high carrier density, [13] representing an exciting opportunity to potentially replace Cu interconnects. In this work, we report The increasing resistance of copper (Cu) interconnects for decreasing dimensions is a major challenge in continued downscaling of integrated circuits beyond the 7 nm technology node as it leads to unacceptable signal delays and power consumption in computing. The resistivity of Cu increases due to electron scattering at surfaces and grain boundaries at the nanoscale. Topological semimetals, owing to their topologically protected surface states and suppressed electron backscattering, are promising candidates to potentially replace current Cu interconnects. Here, we report the unprecedented resistivity scaling of topological metal molybdenum phosphide (MoP) nanowires, and it is shown that the resistivity values are superior to those of nanoscale Cu interconnects <500 nm 2 cross-section areas. The cohesive energy of MoP suggests better stability against electromigration, enabling a barrier-free design . MoP nanowires are more resistant to surface oxidation than the 20 nm thick Cu. The thermal conductivity of MoP is comparable to those of Ru and Co. Most importantly, it is demonstrated that the dimensional scaling of MoP, in terms of line resistance versus total cross-sectional area, is competitive to those of effective Cu with barrier/liner and barrier-less Ru, suggesting MoP is an attractive alternative for the scaling challenge of Cu interconnects.

Synthesis and Future Electronic Applications of Topological Nanomaterials

“…Utilizing phosphine gas, a 1D template of MoO 3 was successfully converted to low resistivity molybdenum phosphide (MoP) metal lines in Figure 4 B and showed superior dimensional scaling with respect to Cu with a TaN barrier, which is not an available phase in the CVD growth of MoP 2 compounds and the nano-molded metastable Mo 4 P 3 phase [ 54 , 55 , 56 ]. A conversion method for WP using 2D chalcogenide templates was also reported, but it resulted in a distorted tungsten phosphide sheet due to the considerable lattice mismatch between WS 2 and WP, as shown in Figure 4 C [ 57 ].…”

“…( E ) Monolayer of WTe 2 converted from ALD-grown WO x thin films. ( B ) Adapted with permission [ 54 ]. Copyright 2023, Wiley-VCH.…”

“…This could potentially lead to a lower line resistance than Cu at the 5 nm technology node [ 36 ]. Moreover, MoP topological metal nanowires were demonstrated as a breakthrough material for interconnect applications, exhibiting superior dimensional scaling of resistivity compared to effective Cu (Cu with a TaN liner) and Ru, as shown in Figure 6 D [ 54 ].…”

“…Precise morphological control is another challenge, as the shape, size, and arrangement of nanostructures influence their electronic properties and functionality. Even though recent studies have explored controlling the size and crystallinity through the nanoconfinement effect in conversion techniques [ 54 , 55 , 112 , 113 ], developing methods to control and manipulate the morphology of topological nanostructures could open up new possibilities for their utilization in electronic devices. Future research should focus on addressing these challenges and exploring innovative approaches to fabricating topological nanostructures with enhanced crystal quality and precise morphological control.…”

“…Copyright 2021, Springer Nature. ( C , D ) Adapted with permission [ 54 ]. Copyright 2023, Wiley-VCH.…”