Interfacial void formation during vapor phase growth of 3C-SiC on Si(001) and Si(111) substrates - Characterization by transmission electron microscopy

The formation and microstructure of voids at the interface between epitaxial films of 3C-SiC on Si(001) and Si(111) substrates have been investigated using cross-sectional transmission electron microscopy. SiC films were deposited using three different techniques; atmospheric pressure chemical vapor deposition (APCVD) in a hot-wall type reactor using the silane-propane-hydrogen system in a substrate temperature (T-s) regime 900 degrees C to 1300 degrees C, reactive magnetron sputtering of Si target in mixed CH4/Ar discharge at T-s = 850 degrees C, and sequential sputtering from Si and C (graphite) targets in pure Ar discharge at T-s between 710 degrees C and 850 degrees C. Voids formed in the Si substrates with primary faceting on {111} planes and increased in size with increasing temperature. Truncation of voids was on {001} and {113} planes as expected from shape equilibrium, but also truncation on apparent {011} facets were observed between inclined {111} planes as an effect of growth kinetics. The presence of voids resulted in an inhomogeneous residual strain state in the films during cooling from the deposition temperature due to thermal mismatch to the substrate as evidenced by a significant broadening of the SiC(002) peak in X-ray diffraction. Corresponding strain relaxation of the SiC film in the absence of voids resulted in plastic deformation of the Si substrate.