Synthesis of SiO2 and SiOxCyHz thin films by microwave plasma CVD

Plasma enhanced chemical vapour deposition of SiO2 and polymeric SiO3C3H5 thin films has been carried out at room temperature in a microwave electron cyclotron resonance (ECR) reactor. Si(CH,),Cl has been used as volatile precursor of Si and pure oxygen as plasma gas. Plasma conditions were characterised by optical emission spectroscopy as a function of the relative flow rates of oxygen and precursor. The oxygen plasma was characterised by emission lines and bands due to O* and O-2(-) species whose relative intensity decreased as the flow rate of the precursor increased. Then, the plasma was dominated by the emission lines of H* species formed by dissociation of the precursor molecules, From the evolution of the intensity of the emission of oxygen and hydrogen lines as a function of the relative concentration of oxygen and precursor and by considering the composition and microstructure of the obtained thin films. a model is proposed for the decomposition mechanism of the precursor. According to this model. Si-Cl bond would dissociate in a first step. Then a series of reactions would follow with the activated oxygen species that, depending on the relative flow rate of oxygen, lead to the formation of SiO2 or a polymeric SiO3C4H2 material. The chemical composition of the films was analysed by Rutherford backscattering spectroscopy (RBS), electron recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS), while their structure and microstructure were investigated by means of transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FF-IR). It has been also shown that the SiO,C,H. thin films, with typical compositions such as Si:1, O:2, C:3.6, H:5.5, yield SiO2 thin films by exposure to a plasma of oxygen. These SiO2 thin films were smoother than the parent SiO3C4H7 samples and the silica films prepared by PECVD under oxygen rich conditions. (C) 2001 Elsevier Science B.V. All rights reserved.