Effects of oxygen content on properties of silicon oxide films prepared at room temperature by sputtering-type electron cyclotron resonance plasma

We present the study of the effects of gas-phase oxygen fraction on properties of silicon oxide films prepared in a sputtering-type electron cyclotron resonance plasma discharge. Dielectric breakdown characteristics of the films are considerably improved by an increase in oxygen flow rate, F_O2, with a constant Ar gas flow rate of 16 sccm. Films prepared at F_O2 of more than 6 sccm have good dielectric breakdown fields of 9-11 MV/cm, which are comparable with those of high quality thermally grown SiO₂. Moreover, the increase of F_O2 improved structural properties of the films. Detailed measurements of their composition and microstructure were carried out using ellipsometry, chemical etch rate measurement in a mixture of HF, H₂O, and HNO₃ (P etch), x-ray photoelectron spectroscopy (XPS), and infrared (IR) spectroscopy techniques. Ellipsometry and XPS measurements indicated that films prepared at F_O2 of more than 3 sccm are stoichiometric. Dependence of the IR spectra and P etch rate on F_O2 of more than 3 sccm indicated that distribution of Si-O-Si bond angle and Si-O bond strain in the films decreases with an increase of F_O2. Based on the behavior of the Si-O-Si bond angle and refractive index of the films, we discuss the improvements in structural properties in terms of growth kinetics.