Origin of Compressive Residual Stress in Polycrystalline Thin Films

Abstract

We present a model for compressive stress generation during thin film growth in which the driving force is an increase in the surface chemical potential caused by the deposition of atoms from the vapor. The increase in surface chemical potential induces atoms to flow into the grain boundary, creating a compressive stress in the film. We develop kinetic equations to describe the stress evolution and dependence on growth parameters. The model is used to explain measurements of relaxation when growth is terminated and the dependence of the steady-state stress on growth rate.

Direct Evidence for Effects of Grain Structure on Reversible Compressive Deposition Stresses in Polycrystalline Gold Films

“…There is general agreement in the literature that the initial tensile stress develops due to elastic strain associated with grain boundary formation during island coalescence [4][5][6][7]. However, a clear consensus has not emerged with respect to the mechanism that leads to the development of the compressive stress [8][9][10][11][12]. An important additional phenomenon observed during growth of continuous films is that the stress state reversibly changes in the tensile direction during interruptions of growth [3,[8][9][10][11][12].…”

“…However, a clear consensus has not emerged with respect to the mechanism that leads to the development of the compressive stress [8][9][10][11][12]. An important additional phenomenon observed during growth of continuous films is that the stress state reversibly changes in the tensile direction during interruptions of growth [3,[8][9][10][11][12]. It seems likely that the origin of these reversible stress changes is linked in some way with the mechanism that leads to development of an overall compressive stress state in thicker films.…”

Morphology evolution of thermally annealed polycrystalline thin films

“…The fact that the stress induced by the intrastructure attraction between the inner grains is mostly relaxed by means of surface currents (plastic effect), whereas that generated by interstructure repulsion is elastically accommodated via generation of strain-that is, the physical parameter investigated to determine the residual intrinsic stress within the samples-would address the compressive nature of the postcoalescence growth stress. The dependence of such a stress on the flux during growth 7,8 (that it is not our case) would be given as a result of transient changes induced by the flux in the equilibrium steady profiles of the gap regions, changes that are relaxed by the surface currents once the flux is stopped.…”

“…Based on these results, we propose a model to address the morphology evolutions in terms of the rising of attractive/repulsive interactions between surface grains. Such a model offers a comprehensive picture of the phenomenon, which allows us to throw light on the origin actually in question [1][2][3][4][5][6][7][8][9] of the postcoalescence compressive stress.…”

“…5,7 Later, Chason et al proposed that the compressive stress in stage (iii) results from surface downhill currents, leading an excess of adatoms into the grain boundaries (GBs) to be inserted. 8 A third model points out the elastic deformation field that experiences a surface on which a density of adatom has been deposited as the cause of the postcoalescence compressive stress. 9 In this paper, we report experimental data concerning the morphology evolution of polycrystalline Au(111) films during thermal annealing.…”