Abstract: A method of reducing impurities in films to be deposited within a chemical vapor deposition (CVD) device includes steps of cleaning the process chamber of the CVD device, and depositing, prior to wafer processing, a gettering layer of, for example, phosphorous containing glass on interior surfaces of the process chamber. The gettering layer getters mobile alkali ions and substantially reduces or prevents outdiffusion of alkali ions and other impurities. The phosphorous containing glass may also be doped with boron. A blocking layer, such as undoped silicate glass, silicon nitride, silicon oxynitride or the like may be deposited on the gettering layer to trap impurities and to prevent phosphorous contamination in a applications sensitive to such contamination.

Abstract: A plasma enhanced chemical vapor deposition process for depositing conformal silicon oxide thin films useful to make thin film transistors which have stable electrical properties and low charge centers onto a substrate comprising flowing a precursor gas mixture of silane and nitrous oxide, the latter at a high rate, at a pressure of at least about 0.8 torr and a temperature of from about 250.degree. to 350.degree. C. The effective volume of the reaction region between the gas manifold inlet and the substrate during processing is kept small.