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 th e structure of epitaxial Si films grown on Si (100) by low-energy de-discha rge plasma enhanced chemical vapour deposition in the temperature range bet ween 410 degrees C and 600 degrees C. The effect of the substrate bias was studied by reflection high-energy electron diffraction, cross-sectional tra nsmission electron microscopy (XTEM) and scanning tunnelling microscopy (ST M). The XTEM investigations showed that the Si films grown at a negative su bstrate bias below 10 V are of good quality and defect free. In the films g rown at a higher negative substrate bias a critical thickness was observed up to which the films remain free of extended defects. This critical thickn ess was found to be related to the ion bombardment of the surface during gr owth 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 fr om two- to three-dimensional at ion energies above 10 eV.