Low Temperature Growth of SiO2 Thin Film by Double-Excitation Photo-CVD

Abstract

A new technique for the low-temperature growth of SiO₂ films has been developed by double-excitation photo-CVD. SiO₂ films can be grown at 30∼240°C from a mixture of Si₂H₆ and O₂ by photo-CVD using a D₂ lamp as a VUV light source, or by double-excitation using an additional Xe lamp or a low-pressure Hg lamp as a UV light source. The growth rate is 90 Å/min in a photo-CVD at 30°C, while deposition does not occur in thermal CVD at 30°C. Concentrations of Si–OH and Si–H bonds can be considerably reduced by the use of photo-excitation. Particularly, double-excitation reduces the oxide-charge density to a large extent and also brings the dielectric constants close to those of thermally-grown SiO₂. The minimum charge density is 5×10¹⁰ cm^-2 in a film deposited at 240°C. The interface state density of a Si MOS diode is also reduced by double-excitation using a Hg lamp in an O₂-excess atmosphere and annealing at 280°C. Its minimum density is 8×10¹⁰ cm^-2eV^-1.