Directional deposition of dielectric silicon oxide by plasma enhanced TEOS process

A description is given of the deposition of dielectric silicon oxide from TEOS in helium/oxygen mixtures in a parallel-plate RF plasma reactor. Under appropriate process conditions, highly directional deposition of low-stress stoichiometric silicon oxide is achieved. The step coverage profiles and the chemical and physical properties of these SiO₂ films were studied to gain an understanding of the origin of preferentially vertical deposition. The typical deposition conditions used in this study were 1 torr total pressure, 320°C substrate temperature, 1-40% TEOS, and 0-80% O₂ in low-power-density (0.1-0.4 W/cm²) 14 MHz RF discharges. Step coverage, chemical stability and film stress were found to be most dependent on the O₂:TEOS gas flow ratio. This dependence can be explained by the various effects involved in the oxide deposition mechanism