Deposition of Fluorine‐Doped Silica Layers from a SiCl4 / SiF4 /  O 2 Gas Mixture by the Plasma‐CVD Method

Silica layers doped with fluorine have been deposited inside a quartz glass tube from a gas mixture. The oxidation reaction was initiated by a nonisothermal microwave plasma maintained at pressures of about 10 Torr and wall temperatures in the region of 1000°–1100°C. From the experiments it was found that fluorine was incorporated in the silica deposit, producing layers with a lower refractive index than that of pure silica. Although the reaction to form from a gas mixture is different from that with , the efficiency of the deposition reaction with is comparable to that with .