Non-linear optical studies of copper diffusion at surfaces and interfaces of microelectronic interconnect structures

Abstract Free surface and solid interface diffusion of copper within microelectronic interconnect structures may mediate significant device degradation mechanisms due to especially fast transport. However, up to now no direct measurements of such diffusion have been made because of difficulties arising from poor signals, interfering signals from the nearly bulk, spurious damage effects from the probe, and other sources. This work reports the first results from an optical method that can overcome these problems: second harmonic microscopy. In this work, non-spatially resolved experiments are first performed to demonstrate a second harmonic response to the diffusive appearance of copper at barrier layer–dielectric interfaces and/or free dielectric surfaces. Second harmonic microscopy is then used to profile lateral copper diffusion along the interfaces and surfaces involving silicon dioxide and silicon nitride.