TIME-DEPENDENT PHENOMENA IN PLASMA-ASSISTED CHEMICAL-VAPOR-DEPOSITIONOF RUGATE OPTICAL FILMS

The plasma-assisted chemical vapor deposition technique was used to pr oduce thin-film structures with both sinusoidally and stepwise varying refractive-index profiles. The refractive index of the SiOxNy system used in the fabrication was found to be time dependent following a ste pwise change in reactant gas flows or initiation of the plasma. This t ime dependence has been quantified using in situ ellipsometry and was found to have components with exponential and linear dependences. The time dependence of water vapor partial pressure in the system was iden tified as the cause of the linear dependence. Allowance for the time-d ependent effects has improved the agreement between the calculated spe ctral response and the measured result for a broadband high-reflectanc e mirror consisting of an arithmetic progression of discrete layers.