Growth of nano-crystalline silicon (nano-Si) films from hydrogen-diluted SiCl4 by the plasma enhanced chemical vapour deposition technique at 250 °C has been studied through mass spectrometry, Langmuir probe diagnostic techniques and Raman spectra measurements. The effects of the hydrogen dilution ratio on the relative densities of SiCln (n = 0–2) in SiCl4/H2 plasma are investigated. The average electron energy (Ee) and electron density (Ne) in SiCl4/H2 plasma increase with the hydrogen dilution ratio till their maxima at 9.25 eV and 3.7 × 109 cm−3, respectively. A suitable hydrogen dilution ratio R (0.4–0.67) is beneficial for the formation of SiCln (n = 0–2) radicals because Ee and Ne both have maxima in this range. More SiCln (n = 0–2) radicals will improve the deposition rate and film quality. In addition, hydrogen radicals play an important role in the surface reaction process. The reaction of H and SiCln (n = 0–2) on the growing surface is beneficial for creating dangling bond sites and prompting the film growth, and the exothermic reaction exothermic energy of H with Cl on the film-growing surface results in the increase of the effective temperature of the film growth.
The growth process of polycrystalline silicon films fabricated at 200 °C by radio-frequency glow discharge plasma-enhanced chemical-vapor deposition technique from hydrogen-diluted SiCl4 has been investigated. We analyze the changes of crystallinity and crystalline grain size with the depth from the top surface of the film through studying the depth profiles of the Raman spectra. The results show that the top surface is composed of silicon nanometer crystalline grains and the clustered amorphous silicon. The component of crystalline phase increases with the increase in depth. Moreover, the film crystallization structure depends strongly on the power. On the other hand, it is almost independent of the substrate temperature and the annealing temperature. Comparing with the growth processes of polycrystalline silicon films from hydrogen-diluted SiH4, it is considered that the formation of nanometer size grains occurs in the gas phase reaction process at the initial stage of film growth, while the grain growth is largely governed by the surface reaction process where in the chlorine element plays an important role.
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