Functionalizing self-assembled monolayers to reduce interface scattering in ruthenium/dielectric for next-generation microelectronic interconnects

Abstract

As the number of transistor increases in modern devices, the resistivity of metal lines increases with the downscaling of the vias dimension due to the increased in surface scattering of electrons. Herein, we evaluated the electrical performance and the adhesion strength of the Ru/SiO2 substrate upon functionalizing with benzyliminetriethoxysilane (BITES) and aminoproyltriethoxysilane (APTES) self-assembled monolayers (SAMs)s at the Ru/SiO2 interface. The covalent bonding and retention of the SAM film on the SiO2 surface were characterized via angle-resolved X-ray Photoelectron Spectroscopy (AR-XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (Tof-SIMS), respectively. According to the Fuchs–Sondheimer (FS) model and scratch test, the specularity parameter and the adhesion strength of the Ru/BITES/SiO2 simultaneously improved after thermal annealing compared to the non-functionalized Ru/SiO2 substrate. The effect of different SAM’s terminal groups (amine and benzylimine) on the electron scattering behavior was investigated based on the formation of an interface dipole upon chemisorption of organic molecules on the metal film. Our results indicate that SAM with the benzylimine terminal group formed a larger positive dipole at the SAM layer of the Ru/BITES/SiO2 interface compared to the Ru/APTES/SiO2, leading to an increased in specular electron scattering events and, thus an enhanced electrical performance of the Ru/BITES/SiO2.