Rapid thermal chemical vapour deposition of SiO_xN_y films

Rapid thermal CVD was utilized to deposit SiO_xN_y layers on III-V materials. The deposition rate and the stoichiometry of the films are controlled by the N₂O partial pressure and the temperature. Deposition rates as high as 100 Å/s can be obtained at 750°C for which the InP substrate is not degraded. The use of N₂O as an adjustable reactant gas allows us to control the stoichiometry of the film by varying the O concentration while the Si and N concentration remain unchanged. This effect may be explained by the dissociation of nitrogen protoxide into oxygen which is directly incorporated in the films and nitrogen in excess in the reaction chamber which increase the dilution. The use of nitrogen protoxide has allowed us to obtain continously all compositions between SiO₂ and Si₃N₄ with indexes of refraction varying between 1.45 and 2.2 Applications to guiding devices are discussed.