Tensile stress evolution during deposition of Volmer-Weber thin films

A simple model is presented that predicts the kinetics of tensile stress ev olution during the deposition of thin films that grow by the Volmer-Weber m echanism. The generation of a tensile stress was attributed to the impingem ent and coalescence of growing islands, while concurrent stress relaxation was assumed to occur via a microstructure-dependent diffusive mechanism. To model the process of island coalescence, finite element methods were emplo yed and yielded average tensile stresses more consistent with experimental observations than those predicted using previously reported analytical mode ls. A computer simulation was developed that models the process of film gro wth as the continuous nucleation of isolated islands, which grow at a const ant rate to impinge and coalesce to form a continuous polycrystalline film. By incorporating the finite element results for stress generation and a mi crostructure-dependent stress relaxation model, the simulation qualitativel y reproduced the complex temperature-dependent trends observed from in situ measurements of stress evolution during the deposition of Ag thin films. T he agreement includes simulation of the decreasing stress relaxation rate o bserved during deposition at increasing temperatures. (C) 2000 American Ins titute of Physics. [S0021-8979(01)01501-8].