Use of SiCl4 as Silicon Precursor for Low-Temperature Halo-Carbon Epitaxial Growth of 4H-SiC
Chlorinated silicon precursor SiCl4 was investigated as an alternative to SiH4 with HCl addition as a source of additional chlorine in order to suppress the homogeneous nucleation during the low-temperature epitaxial growth at 1300°C. The homogeneous nucleation in the gas phase was further reduced compared to SiH4+HCl growth. The process window for obtaining good epilayer morphology during the CH3Cl/SiCl4 growth was found to correspond to Si supply-limited mode. At lower values of C/Si ratio formation of Si-rich polycrystalline islands/droplets took place. At high C/Si ratio, formation of polycrystalline SiC was the source of morphology degradation. The process window became increasingly narrower at higher Rg, which limited the possibility of significantly increasing Rg at such low growth temperatures. Generation of triangular defects became significant at Rg above 5-6 μm/hr, even when a nearly-optimal value of C/Si ratio was used. Similar experiments were conducted using C3H8, a more traditional precursor, instead of the halo-carbon precursor CH3Cl. While a similar growth rate could be achieved for the same SiCl4 flow rate, much lower values of the C/Si ratio were required. The morphology with C3H8 was worse within the process window. The C/Si process window for the C3H8/SiCl4 growth was much narrower compared to the CH3Cl/SiCl4 growth, and the window essentially disappeared at Rg > 3 4 μm/hr.
Anton J. Bauer, Peter Friedrichs, Michael Krieger, Gerhard Pensl, Roland Rupp and Thomas Seyller
S. P. Kotamraju et al., "Use of SiCl4 as Silicon Precursor for Low-Temperature Halo-Carbon Epitaxial Growth of 4H-SiC", Materials Science Forum, Vols. 645-648, pp. 111-114, 2010