Precipitates formation and its impact on the structure of plasma-deposited fluorinated silicon oxide films

Fluorine-doped silicon oxide (SiOF) films prepared by plasma enhanced chemical vapor deposition would generate precipitates on the film surface during exposure to air. The chemical and structural changes of SiOF films during the precipitation process were investigated under various fluorine-doping concentrations in SiOF films. Film composition depth profiles characterized by secondary ion mass spectrometer (SIMS) indicate uneven fluorine distribution within SiOF film after precipitation. During the precipitation process, the Fourier transform infrared (FTIR) spectra of SiOF films showed the decreasing trend in the intensities of Si–Fn (n = 1, 2…) bonding peak, whereas an opposing trend in Si–OH bonding as well as the shoulder peak of Si–O stretching mode were observed. Moreover, the formation of the precipitates lead to lower refractive index, a relief in compressive residual stress, and higher wet etch rate of SiOF films. The structural changes of SiOF films due to the formation of precipitates were extensively discussed.