title: Graphene as an atomically thin barrier to Cu diffusion into Si.
abstract: The evolution of copper-based interconnects requires the realization of an ultrathin diffusion barrier layer between the Cu interconnect and insulating layers. The present work reports the use of atomically thin layer graphene as a diffusion barrier to Cu metallization. The diffusion barrier performance is investigated by varying the grain size and thickness of the graphene layer; single-layer graphene of average grain size 2 ± 1 μm (denoted small-grain SLG), single-layer graphene of average grain size 10 ± 2 μm (denoted large-grain SLG), and multi-layer graphene (MLG) of thickness 5-10 nm. The thermal stability of these barriers is investigated after annealing Cu/small-grain SLG/Si, Cu/large-grain SLG/Si, and Cu/MLG/Si stacks at different temperatures ranging from 500 to 900 °C. X-ray diffraction, transmission electron microscopy, and time-of-flight secondary ion mass spectroscopy analyses confirm that the small-grain SLG barrier is stable after annealing up to 700 °C and that the large-grain SLG and MLG barriers are stable after annealing at 900 °C for 30 min under a mixed Ar and H2 gas atmosphere. The time-dependent dielectric breakdown (TDDB) test is used to evaluate graphene as a Cu diffusion barrier under real device operating conditions, revealing that both large-grain SLG and MLG have excellent barrier performance, while small-grain SLG fails quickly. Notably, the large-grain SLG acts as a better diffusion barrier than the thicker MLG in the TDDB test, indicating that the grain boundary density of a graphene diffusion barrier is more important than its thickness. The near-zero-thickness SLG serves as a promising Cu diffusion barrier for advanced metallization.
authors.affiliation: Nanobio Device Laboratory, School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul, 120-749, Republic of Korea. taeyoon.lee@yonsei.ac.kr.
authors.forename: Juree
authors.initials: J
authors.lastname: Hong
authors.forename: Sanggeun
authors.initials: S
authors.lastname: Lee
authors.forename: Seulah
authors.initials: S
authors.lastname: Lee
authors.forename: Heetak
authors.initials: H
authors.lastname: Han
authors.forename: Chandreswar
authors.initials: C
authors.lastname: Mahata
authors.forename: Han-Wool
authors.initials: HW
authors.lastname: Yeon
authors.forename: Bonwoong
authors.initials: B
authors.lastname: Koo
authors.forename: Seong-Il
authors.initials: SI
authors.lastname: Kim
authors.forename: Taewook
authors.initials: T
authors.lastname: Nam
authors.forename: Kisik
authors.initials: K
authors.lastname: Byun
authors.forename: Byung-Wook
authors.initials: BW
authors.lastname: Min
authors.forename: Young-Woon
authors.initials: YW
authors.lastname: Kim
authors.forename: Hyungjun
authors.initials: H
authors.lastname: Kim
authors.forename: Young-Chang
authors.initials: YC
authors.lastname: Joo
authors.forename: Taeyoon
authors.initials: T
authors.lastname: Lee