Influence of the substrate bias on epitaxial growth of Si films by dc-discharge plasma chemical vapour deposition

We report on the investigation of the influence of the substrate bias on the structure of epitaxial Si films grown on Si (100) by low-energy de-discharge plasma enhanced chemical vapour deposition in the temperature range between 410 degrees C and 600 degrees C. The effect of the substrate bias was studied by reflection high-energy electron diffraction, cross-sectional transmission electron microscopy (XTEM) and scanning tunnelling microscopy (STM). The XTEM investigations showed that the Si films grown at a negative substrate bias below 10 V are of good quality and defect free. In the films grown at a higher negative substrate bias a critical thickness was observed up to which the films remain free of extended defects. This critical thickness was found to be related to the ion bombardment of the surface during growth and to be substrate temperature dependent. The STM studies showed that the nucleation of stacking faults at this critical thickness is connected to an evolution of the surface roughness and a change of the growth mode from two- to three-dimensional at ion energies above 10 eV.