IN-SITU ELLIPSOMETRY AND INFRARED-ANALYSIS OF PECVD SIO2-FILMS DEPOSITED IN AN O-2 TEOS HELICON REACTOR/

Silicon dioxide thin films have been deposited at room temperature on silicon substrates in oxygen/tetraethoxysilane (O-2/TEOS) helicon diff usion plasmas at low pressure (5 mTorr) and 300 W rf power. The proper ties of the films have been measured by in and ex situ ellipsometry, e x situ infrared spectroscopy, and chemical etching (p-etch) as a funct ion of the TEOS flow rate (Q(TEOS)). The growth rate (V-d) is determin ed in situ using an ultra violet-visible phase modulated spectroscopic ellipsometer (1.5 to 5 eV). Two different kinetic regimes appear: at low TEOS flow rate (Q(TEOS) < 5 sccm) V-d increases linearly and no ca rbon species are detected while the OH content rises strongly. For hig her values of Q(TEOS), V-d saturates at approximate to 11 nm. The chan ge in the kinetics corresponds to the appearance of carbon impurities. The increase in the deposition rate is accompanied by a decrease in t he refractive index and an increase in the p-etch rate. The Bruggeman effective medium approximation (BEMA) is used to determine the fractio n of voids incorporated in the layer. It is shown that porous films in corporate water when exposed to the atmosphere. Based on this result, an explanation is proposed for the insensitivity of the stretching pea k of Si-O-Si to the deposition conditions. Good quality SiO2 films wit h optical properties close to that of a thermal oxide can be obtained at low deposition rates (V-d < 5 nm/min). (C) 1997 Elsevier Science B. V.