Effect of water absorption on the residual stress in fluorinated silicon-oxide thin films fabricated by electron-cyclotron-resonance plasma-enhanced chemical-vapor deposition

Fluorinated silicon-oxide (SiOF) films were produced by electron-cyclotron-resonance plasma-enhanced chemical-vapor deposition. The effect of water absorption on the film properties was studied by measuring the residual stress as a function of exposure time to room air. The residual stress shows an increase of the compressive component as the film absorbs water. However, the chemical bonding structure does not change after the water absorption. The residual stress returns to the initial value when the film is dried. It is suggested that the water absorption occurs entirely by physical adsorption of H2O molecules to Si–F bonds.