Residual stress in thin films: effect of processing conditions and microstructure

Thin films develop residual stress during their growth.  Experiments show that the magnitude depends on a balance between different kinetic processes occurring during film growth.  Grain boundary formation can generate tensile stress while insertion of atoms into the grain boundary can make the stress more compressive.  Densification and creation of defects by energetic particles further contributes to the stress.  The balance among these processes is determined by the growth conditions (e.g., temperature, growth rate, pressure) and the microstructure (e.g., grain size).  To understand how these processes influence the stress development, we have performed measurements of stress evolution during growth under different conditions using a wafer curvature technique.  We discuss these results in terms of a kinetic model that we have developed that predicts the dependence of the stress on the processing parameters and microstructure.