Study of copper diffusion into tantalum and tantalum diffusion into copper

Abstract

We have carried out direct diffusion measurements of Cu into Ta and Ta into Cu. Thin films of 50nm thickness of Cu were grown onto a thick Ta layer of 1μm by Ionized Metal Plasma. Samples were annealed in a rapid thermal system from temperatures ranging from 400°C to 800°C for periods of 60s and 180s. The diffusion profile was performed using Secondary ion mass spectroscopy. The Cu diffusion coefficients in Ta can be described by 3.0246 × 10-15 exp (-0.1747eV/kT) at 60s and 2.7532 × 10-15 exp (-0.1737eV/kT) at 180s. The Ta diffusion coefficients in Cu can be described by 2.07051 × 10-15 exp (-0.1773eV/kT) at 60s and 2.1271 × 10-15 exp (-0.1753eV/kT) at 180s. To assure reliability, the extent of both diffusions should be considered in device design and processing.