Mass Transport Mechanism of Cu Species at the Metal/Dielectric Interfaces with a Graphene Barrier

Abstract

The interface between the metal and dielectric is an indispensable part in various electronic devices. The migration of metallic species into the dielectric can adversely affect the reliability of the insulating dielectric and can also form a functional solid-state electrolyte device. In this work, we insert graphene between Cu and SiO2 as a barrier layer and investigate the mass transport mechanism of Cu species through the graphene barrier using density functional theory calculations, second-ion mass spectroscopy (SIMS), capacitance-voltage measurement, and cyclic voltammetry. Our theoretical calculations suggest that the major migration path for Cu species to penetrate through the multiple-layered graphene is the overlapped defects larger than 0.25 nm2. The depth-profile SIMS characterizations indicate that the "critical" thickness of the graphene barrier for completely blocking the Cu migration is 5 times smaller than that of the conventional TaN barrier. Capacitance-voltage and cyclic voltammetry measurement reveal that the electrochemical reactions at the Cu/SiO2 interface become a rate-limiting factor during the bias-temperature stressing process with the use of a graphene barrier. These studies provide a distinct roadmap for designing controllable mass transport in solid-state electrolyte devices with the use of a graphene barrier.

2D Layered Materials for Memristive and Neuromorphic Applications

“…[25] The overgrowth of filaments usually drives excessive ions into inert electrode [91][92][93] and leads to negative-SET behavior in cation-based memristive devices. Graphene has a hexagonal lattice structure with an intrinsic pore size of 0.064 nm, [94][95][96] and the formation energy of defects in the graphene lattice is very high (about 8.0 eV). Graphene has a hexagonal lattice structure with an intrinsic pore size of 0.064 nm, [94][95][96] and the formation energy of defects in the graphene lattice is very high (about 8.0 eV).…”

“…The uncontrollable migration of ions in the active layer under an electric field [31,55,90] would lead to a current-retention dilemma in memristive devices. [90,95] Thus, graphene is an ideal blocking layer to ions diffusion. [90,95] Thus, graphene is an ideal blocking layer to ions diffusion.…”

“…[95] By using two defective graphene Adv. Large operating current and long retention usually coexist in TMO-based memristive devices, which increase the difficulty of fabricating high-speed selectors with large operating current.…”

Review of Graphene as a Solid State Diffusion Barrier

“…In a recent paper by Zhao et al, DFT calculations demonstrated that the potential barrier for a Cu atom to penetrate through the pristine graphene basal plane is as large as 30.62 eV. Defective graphene also has a large potential barrier, with DFT calculations showing for a single carbon vacancy in graphene the barrier is 6.44 eV.…”

Vertical and Lateral Copper Transport through Graphene Layers

“…15 The effectiveness of graphene as a diffusion barrier has been studied from a material characterization standpoint by X-ray diffraction, transmission electron microscopy, and time-of-flight secondary ion mass spectroscopy analyses. 16 A model for Cu transport in graphene barriers has been presented, 17 and the penetration and lateral diffusion of environmental molecules in polycrystalline graphene have been characterized. 18 Nevertheless, most of these works only focused on material characterizations.…”