Relating residual stress to thin film growth processes via a kinetic model and real-time experiments

Abstract

Polycrystalline thin films often have residual stress that is affected by the growth conditions (temperature, deposition rate, etc.) and material parameters. Real-time wafer curvature measurements from many groups have enabled the stress evolution with thickness and its dependence on processing conditions to be quantitatively determined for a large number of systems. Based on these results, we have developed a model for the stress evolution that focuses on the processes that occur at the evolving grain boundary between adjacent grains. The model includes parameters to predict the dependence of the stress on the diffusivity, growth rate, grain size and morphology. In this manuscript, we review the physical basis for this model and compare its predictions with two sets of measurements. In the first case, we consider the evolution of stress in films grown on patterned substrate in which the morphology of the film is known precisely, allowing for direct comparison with the model. In the second case, we consider the steady-state stress as a function of the deposition rate in electrodeposited films.