Momentum effects of the molecular ion beam in SiC crystal growth

Abstract

Silicon carbide (SiC) films were grown on Si(111) substrates by low-energy ion beam deposition for the purpose of investigating momentum effects on crystal growth. Dimethylsilane (SiH 2(CH 3) 2) was ionized to obtain methylsilicenium ions (SiCH 3 +) with Si–C bonding for use as precursors. The ion beam was extracted at 25 m keV for efficient transport from the ion source to the deposition chamber, and SiCH 3 + ions were mass-selected by a sector magnet. Ions transported at high energy were decelerated in front of the substrate to desired energies of 20–100 eV. Ion beam current at the substrate was 0.1–0.2 μA. Temperature at the Si(111) substrate was held at 750 °C during ion beam deposition and pressure in the deposition chamber atmosphere was kept below 3.9×10 −7 Pa. Incident SiCH 3 + ions measured with an energy analyzer were found to have monochromatic energy distributions, e.g. the FWHM was only 1 eV in the case of 100 eV. Crystal structures of the SiC thin films were analyzed in situ by reflection high-energy electron diffraction (RHEED). Under conditions of incident SiCH 3 + ions energies of 60–100 eV, 3C–SiC(111) was grown on Si(111) substrate. On the other hand, under conditions of incident ion energies of 20–50 eV, 2H–SiC was grown on Si(111) substrate. In conclusion, the momentum of low-energy ions was found to exert an effect on the determination of SiC crystal structures.