Compressive Stress Generation in Sn Thin Films and the Role of Grain Boundary Diffusion

Stress evolution in high mobility Sn thin films was measured during electrodeposition and electrochemical etching to understand the roles of grain boundary diffusion and surface conditions in controlling stress. During deposition, the stress reaches a steady-state compressive value that depends on the growth rate. When the deposition or etching conditions were changed abruptly, reversible transients were observed that depend on the film thickness. The results are interpreted in terms of a model based on diffusion of atoms into the grain boundary driven by the chemical potential at the surface.