Residual stresses in silicon dioxide thin films prepared by reactive electron beam evaporation

Abstract

In this study, residual stresses and optical properties of SiO<SUB>2</SUB> films prepared by reactive electron gun evaporation have been investigated as a function of process parameters. The purpose of this work was to find process conditions resulting in SiO<SUB>2</SUB> stress free films or in a stress level balancing the high index material stress in a multilayer structure. We have found that stress in SiO<SUB>2</SUB> films becomes more compressive with conditions resulting in denser coatings (such as high substrate temperatures or low gas pressures). Using an in situ measurement technique, stress stabilities of these films were also studied under vacuum or heated environments. These experiences have confirmed the porous structure of evaporated coatings and have underlined the great importance of water in their final state of stress.