2, University of Georgia, Athens, Georgia, United States
According to the ITRS projections, the level of the current density will soon increase to ~5.35 MA/cm2 at the half-pitch width of 7 nm. There is no existing technology with the breakdown current density high enough to sustain such currents. No feasible interconnect solutions are known for the beyond-the-roadmap nanoscale devices. Scaling deep to the nanoscale range presents problems for conventional metals due to their polycrystalline structure, surface roughness and increased electrical resistivity owing to the electron–boundary scattering. In this presentation, we report the results of our investigation of quasi one-dimensional (1D) van der Waals metals as possible materials for ultimately down-scaled interconnects. Unlike copper some transitional metal trichalcogenides (TMTs) MX3 (where M = Mo, W, and other transition metals; X = S, Se, Te) can be exfoliated or grown into quasi-1D single crystals without grain boundaries, surface roughness or dangling bonds. As a result, the onset of electromigration can be delayed to higher current densities. We have demonstrated prototype interconnects implemented with quasi-1D TaSe3 nanowires with the current density exceeding JB~32 MA/cm2, which is an order of magnitude higher than that for the Cu interconnects . The reliability of the prototype quasi-1D van der Waals metallic interconnects has been tested using the temperature-dependent low-frequency noise (LFN) spectroscopy. The LFN spectrum at elevated temperatures are directly correlated with the electromigration failure mechanisms in interconnects. The LFN data can be used for extracting the information about the vacancy migration along the nanowires and the onset of the electromigration failure. The noise activation energies extracted from the two commonly accepted physical models, the Dutta–Horn model and the empirical noise model in metals, have shown an excellent agreement with the activation energies obtained from the industry standard electromigration mean-time-to-failure (MTF) tests . The obtained results suggest that the quasi-1D van der Waals metals are promising candidates for the ultimately downscaled local interconnects.
This project was supported, in part, by the by the Emerging Frontiers of Research Initiative (EFRI) 2-DARE project: Novel Switching Phenomena in Atomic MX2 Heterostructures for Multifunctional Applications (NSF EFRI-1433395) and by National Science Foundation (NSF) grant #1404967 to A.A.B. on defect engineering in materials.
 M. A. Stolyarov, G. Liu, M. A. Bloodgood, E. Aytan, C. Jiang, R. Samnakay, T. T. Salguero, D. L. Nika, S. L. Rumyantsev, M. S. Shur, K. N. Bozhilov, and A. A. Balandin, “Breakdown current density in h-BN-capped quasi-1D TaSe3 metallic nanowires,” Nanoscale, 8, 15774 (2016).
 G. Liu, S. Rumyantsev, M. A. Bloodgood, T. T. Salguero, M. Shur, and A. A. Balandin, “Low-frequency electronic noise in quasi-1D TaSe3 van der Waals nanowires,” Nano Lett., 17, 377 (2017).