Effect of the predecomposition of SiF4 on the properties of silicon dioxide deposited at low temperatures using SiF4/SiH4/N2O in a double-plasma process

Abstract

A low-temperature (250 °C) plasma deposition process has been developed to prepare silicon dioxide films using SiF4/SiH4/N2O discharge mixtures, decomposing in a separate glow discharge the SiF4 gas just before being fed into the reaction chamber. The deposition rate for these oxides can be higher than 500 Å/min. According to infrared transmittance measurements, the effect of the SiF4 predecomposition is to reduce the amount of hydrogen in the silicon dioxide films. Ellipsometric and chemical etch rate measurements show that films prepared by this approach have better structural properties than those deposited without predecomposing the SiF4 gas. These results suggest that, the silicon–fluorine radicals generated by the predecomposition of the SiF4 gas, change the deposition chemistry in such a way that hinders the incorporation of O–H groups in the films.