High quality 3C-SiC/Si grown on an optimized SiC buffer layer

We describe a procedure for the optimization of a 3C-SiC buffer layer for the deposition of 3C-SiC / (001) Si. After a standard carbonization at 1125 °C, we deposited a 100 - 150 nm thick SiC buffer with varying SiH4 and C3H8 flow rates at 200 mbar, while the temperature was increased from 1125 °C to the growth temperature of 1380 °C. Different heating rates and precursor flows were tested, which influenced the quality and the crystallinity of the buffer layer and the presence of voids at the SiC/Si interface. The buffer layers were studied by stopping the growth at 1380 °C, just before thick SiC film growth, and analyzed by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Raman,Transmission Electron Microscopy (TEM), X-Ray- Photoelectron Spectroscopy (XPS) and X-Ray Diffraction. By the optimization of the growth conditions, in particular by using a slow heating ramp (21.5 °C / min) and higher precursor rate, interfacial voids were greatly reduced (fig.1) and the crystallinity was improved, with the appearance of a (002) SiC peak in the XRD spectra with FWHM of about 1400 arcsec. To demonstrate the effectiveness of the described procedure, on the optimized buffer (labeled B in fig. 1) a high-quality 1.5 ?m 3C-SiC was grown using SiH4 and C3H8 with Si/C=1.4 at 1380 °C and 200 mbar, with excellent surface morphology (roughness < 1 nm on 1x1 ?m2 scale) as measured by AFM, good crystallinity as measured by XRD (FWHM of about 790 arcsec), XPS and TEM (fig. 2) and low stress, as indicated by Raman measurements: considering the positions of the LO and TO peaks in the film compared to the bulk we calculated a residual tensile strain of about 0.03%.