Low-temperature homoepitaxial growth of 4H–SiC with CH3Cl and SiCl4 precursors

In prior research, a possibility to increase the growth rate of the low-temperature epitaxial growth of 4H–SiC was explored by supplementing chloro-carbon precursor CH3Cl with HCl as an additional source of chlorine. In the current work, SiCl4 was investigated as a replacement for SiH4+HCl. The homogeneous nucleation in the gas phase was further reduced compared to SiH4+HCl growth, thus essentially eliminating the main bottleneck for increasing the growth rate (Rg). However, for low values of the carrier gas flow, premature dissociation of Si gas-phase clusters was found to cause Rg non-homogeneity and triangular defect formation. The drastically suppressed homogeneous nucleation opened the window for increasing the carrier gas flow velocity in order to improve the Rg homogeneity from upstream to downstream. Nevertheless, generation of triangular defects was significant at Rg above 5–6 μm/h. The process window for obtaining good epilayer morphology was found to correspond to Si supply-limited mode. The window was restricted at low values of C/Si ratio by formation of Si-rich islands/droplet and at high C/Si ratio by formation of polycrystalline SiC. The process window became increasingly narrower at higher Rg, which serves as a new bottleneck for significantly increasing Rg at such low growth temperatures.