Low-temperature plasma enhanced chemical vapor deposition of SiO ₂

Silicon dioxide (SiO₂) films, with qualities approaching to those of thermal oxide, were deposited at 40°C in a helical resonator plasma reactor from tetraethylorthosilicate (TEOS) and oxygen discharge. The films were characterized using transmission infrared spectroscopy, variable angle spectroscopic ellisometry, and wet etch rate measurements. It was found that the TEOS/O₂ ratio, @FR, in plasma enhanced chemical vapor deposition of SiO₂ is as important a parameter as the substrate temperature. Using low TEOS/O₂ ratio (@FR <1:20), high quality SiO₂ films could be deposited by PECVD at room temperature. At high TEOS/O₂ ratio, particularly at low temperature, ethoxy ligands of the TEOS molecule are incorporated into the film disrupting the connectedness of the SiO₄ tetrahedra resulting in porous, low density films with high OH content.