LOW-PRESSURE CHEMICAL VAPOR-DEPOSITION OF THIN-FILM GEO2-SIO2 GLASSES

Films of germania-silica glasses were prepared by low pressure chemical vapor deposition using a horizontal tube-type reactor. The design and operating principles of the system are described, as are the kinetics and properties of the deposited glass films. The films were grown at different temperatures (250°–600°C), at different flow rates (30–60 seem) and at different gas-phase ratios of SiH4 and GeH4. It was found that under otherwise similar reactor conditions, the deposition rate is much greater for higher silane to germane gas ratios. It was also found that SiH4 catalyzes the decomposition of GeH4. Studies of the deposited films show that their index of refraction changes linearly with a change in solid-phase composition, and that the stress of these films, as deposited on silicon (100) substrates, varies between 108–109 dyne/cm2 when the mole fraction GeO2 incorporated in the film varies from 1.0 to 0.0. © 1990, The Electrochemical Society, Inc. All rights reserved.