Surface diffusion of copper on tantalum substrates by Ostwald ripening

In this work, we report on the determination of surface diffusion coefficient of copper on tantalum substrates by Ostwald ripening. It is shown that impurities, such as oxygen, strongly influence the kinetics of dewetting of copper films on tantalum substrates. Two technologically important interfaces with copper were investigated: Cu/beta-Ta and Cu/alpha-Ta. For copper surface diffusion on beta-Ta surface, a surface diffusion coefficient of D-S(betaTa) = 2.6(1.0)(3.7) (.) 10(-11) (cm(2)/s) was measured at 550 degrees C. The temperature dependence of surface diffusion was investigated between 400 degrees C and 550 degrees C. Using an Arrhenius relationship, an activation energy of 0.83 +/- 0.1 eV and a pre-exponential factor of D-S0(betaTa) = 2.8(0.2)(7.5) (.) 10(-6)(cm(2)/s) were calculated. For copper surface diffusion on alpha-Ta surface, a diffusion coefficient of D-S(alphaTa) = 2.0(1.5)(3.1) (.) 10(-12)(cm(2)/s) was measured at 550 degrees C. We discuss the diffusion mechanism involved during the cluster growth and the origin of the faster surface diffusion of copper on the beta-Ta substrate as compared to the alpha-Ta phase. (c) 2006 Elsevier B.V. All rights reserved.