Design, construction and operation of a PECVD system and development of GeO(2)-SiO(2) thin film glass dielectrics by low pressure chemical vapor deposition

Films of germania - silica (germanosilicate) glasses were prepared by low pressure chemical vapor deposition using a horizontal tube-type reactor over the temperature range of 250{dollar}spcirc{dollar}C to 700{dollar}spcirc{dollar}C. The design and operating principals of the system are described, as are the kinetics and properties of the deposited glass films. The films were grown at different flow rates (30-60sccm), and at different gas phase ratios of SiH{dollar}sb4{dollar} and GeH{dollar}sb4{dollar}. 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 SiH{dollar}sb4{dollar} 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 10{dollar}sp8{dollar}-10{dollar}sp9{dollar}dyne/cm{dollar}sp2{dollar} when the mole fraction GeO{dollar}sb2{dollar} incorporated in the film varies from 1.0 to 0.0.; Results of the initial trials to use plasma enhancement in the deposition of the layers are also included. These studies suggest that the plasmas generated using coil electrodes are more intense than the ones with ring or capacitive elctrodes. Using the system in the PECVD mode to deposit GeO{dollar}sb2{dollar}-SiO{dollar}sb2{dollar} films, it was found that the deposition rate is much higher for this case than for the LPCVD films deposited at the same temperature. Trench filling, reflow, and conformality characteristics of these films are also studied.