Effect of hydrogen dilution on the remote plasma enhanced chemical vapor deposition of chlorinated SiO₂ films

Chlorinated silicon dioxide films have been prepared at low temperatures (200 °C) and high deposition rates (900–1700 Å/min) by remote plasma enhanced chemical vapor deposition using mixtures of SiCl₄, O₂, Ar, and H₂ under various hydrogen flow rate conditions. It was found that films deposited without hydrogen grow with the highest deposition rate, however they exhibit poor properties such as high etch rate, low density, and low refractive index. These oxides are also chemically unstable and easily hydrolyzable upon exposure to ambient moisture. It is assumed that the low chlorine content (detected by Rutherford backscattering) in these samples is due to the hydration of the weak Si–Cl bonds existing in the as-deposited films, which generates desorption of HCl and forms the Si–OH bonds observed in the corresponding infrared spectra. The addition of hydrogen to the process reduces the deposition rate but improves the properties and stability of the films by reducing the amount of chlorine incorporated during growth. At hydrogen flow rates moderately higher than the SiCl₄ flow, dense and stable chlorinated oxides with properties close to stoichiometric SiO₂ are obtained. The composition results indicate that in order to obtain these types of oxides the chlorine concentration should be limited to a value around 2.6 at. %. © 1998 American Vacuum Society.