Yasushi Inoue, Yasunori Takahara, Hiroyuki Sugimura and Osamu Takai

Department of Materials Processing Engineering, Nagoya University
Nagoya 464--8603, Japan
inoue@numse.nagoya-u.ac.jp

Plasma-enhanced chemical vapor deposition (PECVD) process using organosilicon reactants were diagnosed by in situ mass and infrared spectroscopy. We used a PECVD system with an rf-plasma source which consisted of a quartz glass cylinder and a 3.5 turn inductively-coupled coil. Tetramethylsilane (TMS) or tetramethoxysilane (TMOS) was introduced from a gas inlet on the side wall of the deposition chamber. An oxygen gas was also introduced from the other gas inlet at the top of the plasma source. The partial pressure ratio of oxygen to a constant total pressure of 10~Pa, R, was varied from 0~80%. The temperature of Si (100) substrates was kept at room temperature. Gaseous species around the substrate were analyzed by a quadrapole mass spectrometer (QMS). In situ measurement for both the gas phase and the film surface by Fourier transform infrared spectroscopy was also performed.

The mass analyses in the plasma revealed that the oxygen gas was preferentially consumed by methyl functional groups in the reactant molecules to produce CO. The region of R in which the oxygen molecules were detected by QMS at the mass number of 32 resulted in the deposited films with the carbon content of almost zero. Monitoring the quantity of the oxygen molecules by QMS is a very easy and useful way to synthesize carbon-free silicon dioxide films.