Crystal Growth of Free Standing 3C-SiC Using Air-Bridge Structure

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Silicon carbide(SiC) is a promising material for the next generation. Among SiC polytypes, Cubic SiC (3C-SiC) has advanced electrical properties, like high low-field electron mobility and high saturated electron drift velocity. Heteroepitaxial growth of 3C-SiC on Si substrates allows a significant cost advantage in the fabrication of large-diameter wafers. However, the lower quality of this material grown heteroepitaxially on Si has hindered its development. A large number of defects such as misfit dislocations, twins, stacking faults and cracks have been identified at the SiC/Si interface, owning to the mismatches in both the lattice constant and the thermal expansion coefficients between the 3C-SiC films and Si substrates.This study reports on heteroepitaxial growth of 3C-SiC on Si substrate with air-bridge structure in order to reduce the high density of defects and the strain in the 3C-SiC epilayer. It has been necessary to investigate the epitaxial growth close to the 3C-SiC/Si in … More terface. 3C-SiC layer was grown mainly on a (111)-oriented silicon substrate by using Si2(CH3)6 (Hexamathyldisilane : HMDS). The crystallinity and surface morphology of 3C-SiC grown on Si(111) depended on the carbonization process. The diameter of each 3C-SiC island depended on the temperature of CVD growth at an early stage of epitaxial growth of 3C-SiC on Si substrate.Three-dimensional fine was formed by using "micro-channel epitaxy(MCE)", "facet-initiated lateral epitaxial overgrowth(FILEO)", "air-bridged structural growth(ASG)" and "lateral epitaxial overgrowth(LEO)". FILEO, ASG and LEO have the fabrication procedure within two CVD growth steps. The crystallinity of ELO formed in MCE became like polycrystalline without the control of nucleation and growth. In FILEO, triangular pyramid of 3C-SiC was formed by {110} facet, owning to the difference of growth rate along between [110] and [111] direction. The crystallinity of bridged regions above air-gap was improved from Raman spectra, compared with seed regions combined Si substrate in ASG. The crystallinity of ELO regions was inferior to that of seed regions in LEO. This result may be improved by close control of experimental parameters at initial stage of 3C-SiC grown on Si substrates. Less