Nanocomposite low-k SiCOH films by direct PECVD using vinyltrimethylsilane

Vinyltrimethylsilane (VTMS) was used as a precursor for the deposition of SiCOH films by direct and remote plasma-enhanced chemical vapor deposition (PECVD). Film property was compared with films prepared with tetramethylsilane (4MS). As-deposited films and the films annealed at 450 degreesC have been characterized. The growth rate decreased with increasing substrate temperature and increased with increasing O-2/precursor ratio and plasma power. The dielectric constant was inversely proportional to the relative carbon content and the film deposited with VTMS had higher carbon content. The refractive index of the as-deposited films with VTMS was about 1.46-1.44 and decreased to 1.40 after annealing. The reduction of the refractive index seemed to be due to the lower density and increased porosity of the film. After annealing, the film formed with VTMS showed lower dielectric constant than the film with 4MS. It is believed that a thermally unstable phase in the film was formed more favorably with vinyl groups in VTMS, and the desorption of the unstable phase during postannealing process makes additional nanopores in the film. The SiCOH films from VTMS showed a low dielectric constant of 2.0 at an optimum condition. (C) 2004 The Electrochemical Society.