Degree Granting Department
Stephen E. Saddow, Ph.D.
Silicon carbide, Heteroepitaxy, Crystal defects, Chemical vapor deposition, Polysilicon
The heteroepitaxial growth of cubic silicon carbide (3C-SiC) on (111) silicon (Si) substrates, via a horizontal hot-wall chemical vapor deposition (CVD) reactor, has been achieved. Growth was conducted using a two step process: first the Si substrate surface is converted to SiC via a carbonization process and second the growth of 3C-SiC is performed on the initial carbonized layer. During carbonization, the surface of the Si is converted to 3C-SiC, which helps to minimize the stress in the growing crystal. Propane (C3H8) and silane (SiH4), diluted in hydrogen (H2), were used as the carbon and silicon source, respectively. A deposition rate of approximately 10 µm/h was established during the initial process at a temperature of ~1380 °C. The optimized process produced films with X-ray rocking curve full-width at half-maximum (FWHM) values of 219 arcsec, which is significantly better than any other published results in the literature.
Once this process was developed a lower temperature process was developed at a slower growth rate of ~2 µm/h at 1225 °C. The crystal quality was inferior at the reduced temperature but this new process allows for the growth of 3C-SiC(111) films on oxide release layers for MEMS applications. In addition, for electronic device applications, a lower temperature process reduces the generation of defects caused by the nearly 8 % mismatch in the coefficient of thermal expansion (CTE) between 3C-SiC and Si. Finally a new process using a poly-Si seed layer deposited on an oxide-coated Si wafer was used to form 3C-SiC films for MEMS applications. The results indicated initially that the films may even be monocrystalline (based on X-ray evaluation) but later analysis performed using TEM indicated they were highly-ordered polycrystalline films. The grown 3C-SiC films were analyzed using a variety of characterization techniques.
The thickness of the films was assessed through Fourier Transform infrared (FTIR) spectroscopy, and confirmed (in the case of growth on poly-Si seed layers) by cross-section scanning electron microscopy (SEM). The SEM cross-sections were also used to investigate the 3C-SiC/oxide interface. The surface morphology of the films was inspected via Nomarsky interference optical microscopy, atomic force microscopy (AFM), and SEM. The crystalline quality of the films was determined through X-ray diffraction (XRD).
Scholar Commons Citation
Locke, Christopher, "Growth of 3C-SiC on (111)Si using hot-wall chemical vapor deposition" (2009). Graduate Theses and Dissertations.