Effect of substrate bias on Si epitaxial growth using sputtering-type electron cyclotron resonance (ECR) plasma

Control of the energy of ions hitting the substrate during in situ cleaning and deposition was found to be very important for deposition of epitaxial Si thin film. This was studied by applying a substrate bias in the range of -30 to +30 V in a sputtering-type electron cyclotron resonance (ECR) plasma system. During in situ, cleaning, positive bias voltage reduced the ion bombardment energy, and resulted in epitaxial deposition of Si crystal film even at a low gas pressure of 0.8 mTorr, at which epitaxial deposition was not possible previously. During deposition, obvious improvements in the crystallinity of the epitaxial Si film were achieved when the ion energy was reduced by applying a positive bias. On the other hand, application of a negative bias for the deposition process resulted in amorphous film even when deposition was performed at the high gas pressure of 1.7 mTorr, at which epitaxial deposition was possible previously.