Polycrystalline and amorphous Si-C films were prepared by rf glow-discharge decomposition of silane-methane mixtures at 700 °C. We have demonstrated that polycrystalline SiC films with large grains grow under heavy hydrogen dilution. The bonding properties as a function of film composition and hydrogen dilution were characterized by means of x-ray diffraction and x-ray photoelectron spectroscopy. Crystallization takes place at around C content x=0.5 in Si1−xCx, accompanying some segregation of carbon atoms in grain boundaries, as a result of a preference for heteronuclear bonds. It was shown that C-C(C3−nSin) (n=0–3) bonds appear in the carbidic phase of C-rich films, leading to occurrence of compressive strain in the crystalline SiC grains. In addition, effects of hydrogen dilution were discussed in correlation with the strain.

Doped polycrystalline SiC films were deposited from a SiH4-CH4-H2-(PH3 or N2) mixture by plasma-enhanced chemical vapor deposition at 700 °C. The best crystallinity was obtained at x∼0.53 in Si1−xCx for both undoped and doped films. The crystallinity was enhanced by both P and N doping, but deteriorated again under high doping conditions. Also, better crystallinity was obtained by doping with P rather than N. Intrinsic tensile and compressive stresses were observed for P- and N-doped films, respectively. The resistivity and dangling-bond density decreased in correspondence to the enhancement in crystallinity. Origins of the dangling bonds and of a change in the crystallinity were discussed.

Using x-ray diffraction and electron-spin-resonance measurements, the crystal structure and bonding configurations of Si1−xCx films by plasma-enhanced chemical vapor deposition at 700 °C are shown to change abruptly at around x=0.5. At around this composition, a polycrystalline film with a cubic SiC 〈111〉 preferred orientation and an average grain size of 95 nm is grown on a fused silica substrate under high hydrogen dilution. The structural change can be attributed to an increase in the probability of occurrence of a Si- C4 tetrahedron in a chemically ordered network.

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