Thermal stability of Pt bottom electrodes for ferroelectric capacitors

The stress of Pt films deposited at various temperatures and its correlation with the formation of hillocks during heat treatment were investigated. The residual stress changes from compressive to tensile as the deposition temperature increases. The compressive residual stress of a Pt film deposited at room temperature is initially relaxed by the shrinkage of the film thickness and then by hillock formation at a certain maximum compressive stress when the Pt film is heat-treated. On the other hand, Pt films deposited at higher temperatures (up to 500 °C) have a high tensile residual stress. The Pt film maintains its smooth surface and no hillocks appear during the heat treatment at 500 °C when the residual stress is tensile, since the threshold temperature at which hillocks form increases.