Determining polytype composition of silicon carbide films by UV ellipsometry

Resumo

A universal ellipsometric model is proposed that describes the optical properties of silicon carbide (SiC) films grown on Si substrates by the method of atomic substitution due to a chemical reaction between the substrate and gaseous carbon monoxide. According to the proposed three-layer model, Si concentration decreases in a stepwise manner from the substrate to SiC film surface. The ellipsometric curves of SiC/Si(111), SiC/Si(100), and SiC/Si(110) samples grown under otherwise identical conditions have been measured in a 1.35–9.25 eV range using a VUV-VASE (J.A. Woollam Co.) ellipsometer with a rotating analyzer. Processing of the obtained spectra in the framework of the proposed model allowed the polytype composition of SiC films to be determined for the first time. It is established that SiC grown on Si(111) is predominantly cubic, while SiC on Si(110) is predominantly hexagonal (with cubic polytype admixture) and SiC on Si(100) has a mixed polytype composition.