Structural and electrical properties for fluorine-doped silicon oxide films prepared by biased helicon-plasma chemical vapor deposition

Fluorine-doped silicon oxide (SiOF) films, prepared using biased helicon-plasma chemical vapor deposition, are investigated to clarify the relationship between their bond structures and electrical properties. For this purpose, C-V characteristics, I-V characteristics, FT-IR and Raman spectra were measured. In this investigation, two kinds of SiOF films prepared with SiF4 flow ratios of 0.5 and 1.0 were compared. The SiOF film prepared with a SiF4 flow ratio of 0.5 has a low leakage current and its relative dielectric constant is 3.6, whereas the film prepared with a SiF4 flow ratio of 1.0 has a high leakage current and its relative dielectric constant is 3.2. FT-IR and Raman spectra studies clarify the following: (1) The SiOF film with a low leakage current contains SI-F bonds, as well as 3-fold or 4-fold rings. (2) The SiOF film with a high leakage current contains F-Si-F bonds or near-neighbor Si-F bonds in addition to Si-F bonds, but it does not contain 3-fold or 4-fold rings.