Silicon dioxide films fabricated by ECR microwave plasmas

Silicon dioxide films were deposited on crystalline silicon substrates by microwave plasma-enhanced CVD. An axial DC magnetic field in the plasma chamber produced electron cyclotron resonance (ECR) conditions at an excitation frequency of 2.45 GHz. Films were grown on Si ⟨100⟩ substrates at a temperature of 140-600°C, flow rates of 0.5-10 SCCM SiH₄ and 10-30 SCCM O₂, and at a pressure of 10^-3 torr. Infrared absorption spectroscopy of the samples indicated no detectable SiH, SiH₂, or SiOH groups. As the plasma-substrate separation varied from 5 to 25 cm, the index of refraction decreased from approximately 1.47 to 1.44 and the growth rate decreased from 160 to 60 Å/min. Films grown under optimal conditions had infrared absorption spectra nearly identical to those of thermally grown oxides and an index of refraction of 1.456. The authors conclude that using an ECR microwave plasma, SiO₂ films with optical and bonding properties comparable to oxides thermally grown at 1000°C in dry oxygen can be deposited at low temperature (350°C) and low pressure (10^-3 torr) utilizing SiH₄ and O₂ without the need for a carrier gas