Nobuyuki Kanayama

Epitaxial growth of 3C-SiC on Si(111) using hexamethyldisilane and tetraethylsilane

Hexamethyldisilane (HMDS, Si2(CH3)6) and tetraethylsilane (TES, Si(C2H5)4) were used as safe organosilane sources for the chemical vapor deposition of SiC films on Si(111) substrates. The surface morphology and crystalline quality of SiC films were investigated. On increasing temperature in H2 ambient after carbonization, voids appeared at the interface of SiC/Si causing the formation of hillocks on the grown SiC films. The formation of voids was prevented by supplying C3H8 and HMDS or TES during the heating process to the growth temperature, leading to the growth of SiC films with a good surface morphology. In the case of TES, the excess carbon incorporated in the film due to the high C/Si ratio was removed by reducing TES flow rate. It was found that the control of the flow rate of organosilane sources during heating plays a vital role in the formation of a high-quality SiC film with a smooth surface.

Spectroscopic Ellipsometry of 3C-SiC Thin Films Grown on Si Substrates Using Organosilane Sources

Dielectric function spectra of 3C-SiC films on Si substrates in the energy region of 0.73–6.43 eV were measured by spectroscopic ellipsometry. Hexamethyldisilane (Si2(CH3)6) and tetraethylsilane (Si(C2H5)4) were used as safe organosilane sources for the growth of SiC films. The measured spectra were compared with those of 3C-SiC on a Si(001) substrate grown with disilane (Si2H6). First, the pseudodielectric function spectra gave a shoulder structure corresponding to the direct X5–X1 interband transition in the Brillouin zone. Secondly, the dielectric function of 3C-SiC was determined by applying a four-layer model in which we took into account the surface roughness and mixed crystals of a carbonized interface layer. Finally, the third-derivative lineshape of the imaginary part e2 of the complex-dielectric function provided the values of the interband transition energy Eg and the broadening parameter Γ for the X5–X1 interband transition. The measured values of Γ indicated that the crystalline quality of SiC films grown using organosilane sources is comparable to that of SiC films grown using Si2H6.

Plasma-Carburizing of Powder Metallurgy Chromium

Plasma-carburizing treatment of powder metallurgy chromium was carried out and the following results were obtained.1) X-ray diffraction analysis showed the formation of Cr3C2, Cr7C3 and Cr23C6.2) Cr23C6 was formed in the surface at the early stages of the carburizing process, but Cr7C3 and Cr3C2 were formed as treatment proceeded.3) The thickness of the carbide layer was proportional to the square root of treatment time