The various low dielectric constant materials have been widely studied as alternaves to silicon dioxide (Si$O_2$) films. Among them, the fluorinated silicon oxide (SiOF) film has attracted much attentions as new interlayer dielectrics since it exhibits a lower dielectric constant than Si$O_2$. In this study, we have prepared the SiOF films by electron cyclotron resonance plasma enchanced chemical vapor deposition (ECR PECVD) method, and observed the dependence of film properties on the deposition variables of Si$F_4$ flow rate, substrate temperature, microwave power, and pressure. The increase of F contents with an increasing the flow rate of Si$F_4$ has led to the decrease of dielectric constants, which is thought to be due to the decrease in ionic polarization by Si-O structural changes rather than due to the decrease in electronic polarization. The properties of films have not exhibit a dependence on substrate temperaures in the range of 25 ~ 200℃. When the microwave power is as low as 300 W and the pressure is higher than 5 mTorr, the Si-$F_2$ bonds have been formed in films. Since Si-$F_2$ bonds have been reported to play a great role in water absorptions, the deposition conditions at which these bonds is formed need to be avoided.
The fluorinated silicon oxide (SiOF) film with a low dielectric constant is hygroscopic, which leads to the increase in the dielectric constant by the formation of highly polar -OH bonds in the film. We prepared SiOF films by electron cyclotron resonance enhanced chemical vapor deposition (ECR PECVD) with precursors of Si$H_4$ (0, 0.5, 1.5 sccm) / Si$F_4$ (8 sccm) / $O_2$ (16 sccm), and investigated the effect of hydrogen on the dielectric stability of films. The Si-$F_2$ bonds has been reported to be a significant factor in water absorption, and confirmed in this work. It was also found, in our study, that Si-O-Si bonds around free volumes are closely related to the hygroscopicity of films. It was observed that the films deposited with Si$H_4$ addition exhibit a higher resistance to water absorption than those deposited without it. The hydrogen radicals dissociated from Si$H_4$ are considered to suppress the formation of Si-$F_2$ bonds by scavenging F from Si$F_2$ radicals. The hydration of Si-O-Si bonds around free volumes is also prevented by the addition of Si$H_4$ because reduces the free volume formation is suppressed due to the removal of excessive fluorines by hydrogen.