J. Phys. IV France 05 (1995) C5-1005-C5-1011
LPCVD SiO2 Layers Prepared from SiH4 and O2 at 450 °C in a Rapid Thermal Processing ReactorC. Cobianu1, J.B. Rem2, J.H. Klootwijk2, M.H.H. Weusthof2, J. Holleman2 and P.H. Woerlee2
1 Institute of Microtechnology, P.O. Box 27-17, 77550 Bucharest, Romania
2 University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
In this paper experimental results of the silane oxidation kinetics in a rapid thermal low pressure chemical vapor deposition (RTLPCVD) cold wall reactor at 450 °C are presented. For a certain total pressure kept constant in the range of 0.6-4.5 mbar. it is always found a certain threshold silane partial pressure p(th)SiH4 (decreasing from 0.15 mbar to 0.076 mbar when the total pressure increases) which determines a sharp transition from no film formation to high deposition rates of the SiO2 layers. Critical partial pressures for lower limits of explosion at room temperature (0.223 mbar) and at deposition temperature (0.17 mbar) are noticed. The film deposition is very sensitive to the changes in the chemical state of the walls. These results may indicate that the silane oxidation process is controlled by the gas phase chain reactions. By keeping constant the total pressure (4.5 mbar), the SiH4 partial pressure (0.079 mbar) and the total gas flow rate (570 sccm), with the nitrogen varied as a gas balance, an increase-maximum-decrease dependence of deposition rate as a function of O2/SiH4 mole ratio is found. Uniform SiO2 layers (5% around the averaged value) were found for the above CVD conditions and an O2/SiH4 ratio equal to 11. Without further process and equipment improvements this process cannot be used in practice.
© EDP Sciences 1995