Research on the epitaxial growth of silicon carbide on silicon and aluminum nitride.

摘要

Silicon carbide is one of the most suitable semiconductors for high-temperature, high-speed, high-frequency and high power applications. In this thesis, heteroepitaxial growth of 3C-SiC is demonstrated on various substrates including Si(100), Si(111), patterned Si and AlN/sapphire using a HMDS + (H₂+Ar) gas mixture.; Single crystals of 3C-SiC were grown by a two-step process on Si(100) and Si(111) substrates using hexamethyldisilane (HMDS) as the source. No separate carbonization step was required despite the fact that previous attempts usually utilized a separate carbonization step. The first step, “nucleation stage”, was optimized at a temperature of 1250°C for a duration of 2 min for the conditions that would yield single crystalline 3C-SiC film. The second step, “growth stage”, proceeded at a higher temperature of 1380°C. Furthermore, growth was carried out on Si(111) substrates for comparison with growth on (100) substrates. In both cases the orientation relationship between the film and the substrate was parallel epitaxy. However, the higher reproducibility (i.e. the higher probability of achieving single crystal 3C-SiC at the optimum condition) of epitaxial growth on Si(111) compared to Si(100) was interpreted to mean easier growth on the Si(111) substrate. Two possible explanations, one in terms of surface reconstruction and the other in terms of surface energy considerations, were proposed to explain these observations.; Low-temperature epitaxial growth of 3C-SiC on Si was achieved by a one-step process by introducing trimethylgallium during growth. The addition of TMG significantly influenced the growth by: (i) allowing the epitaxial growth temperature to be lowered to 1200°C, and (ii) increasing the growth rate at a given temperature. These suggest that TMG could be acting as surfactant in the 3C-SiC/Si system.; Growth of SiC on AlN/sapphire substrates was demonstrated. The effect of growth temperature on the SiC crystal quality (i.e. poly or single crystal) and the influence of the underlying AlN layer thickness on the SiC surface morphology were investigated. Despite the fact that the underlying AlN layer has a wurtzite structure, the SiC film grew with a zincblende structure.; Finally, selective deposition of SiC on patterned Si substrates was studied using SiO₂ as a mask material. Perfect selectivity (i.e. no SiC nuclei over mask) was achieved by adding HCl to the carrier gas at 1200°C. HCl etches adatoms deposited on the mask surface.