Abstract

The mechanical properties of thin films are strongly dependent on structure, micro structure, physicochemical activity, and composition. They can be influenced by the production technology and the parameters chosen. Relatively low intrinsic tensile stresses in the 10⁸-dyn·cm^-2 range occur in ~50-nm thick Ag and Al films made by fast evaporation and condensation in nonreactive high vacuum. Cr films show much higher values of ~10¹⁰ dyn·cm^-2. In oxygen doped Cr and Al films the stress decreases and in Al films even changes sign, becoming compressive. Further oxygen supply decreases the compressive stress and, by reactive deposition, favors the formation of tensile stressed Al₂O₃ films. Quarterwave thick dielectrics are often tensile stressed when low refractive and compressive when high refractive. Intrinsic stresses may be masked by thermal effects due to a high temperature of preparation and be influenced by H₂O sorption and grain boundary segregation effects. Dielectric films prepared by sputtering, ion assisted deposition, and ion plating show compressive stresses in the 10⁹-dyn·cm^-2 range for metal oxides and 10¹⁰ dyn·cm^-2 for nitrides. Stress can be reduced by use of lower bombarding ion and coating material energy during film growth.

© 1989 Optical Society of America