Solid State Reaction in Sandwich Type Al/Cu Thin-Films

Al/Cu/Al and Cu/Al/Cu triple layers with approximately 10 nm single layer thickness were deposited by ion beam sputtering onto needle shaped W tips and analyzed in the early stages by means of atom probe tomography (APT) using a pulse frequency of 2000 Hz. For comparison reaction couples were also deposited onto highly doped [100] silicon planar substrates. Specimens were prepared using a dual beam focused ion beam (DB-FIB), APT and TEM. Macroscopic diffusion experiments were performed to obtain interdiffusion coefficients and is compared with the ones derived from the APT measurements. For that, cylindrically shaped Al and Cu disks were clamped together and isothermally annealed at 410degC and 525degC. After each time step the samples are mechanically polished and composition profiles are determined perpendicular to the initial interface by using energy dispersive X-ray microanalysis (EDX)