Silicon oxynitride thin films synthesised by the reactive gas pulsing process using rectangular pulses

Silicon oxynitride thin films were synthesised by the reactive gas pulsing process using an argon, oxygen and nitrogen gas mixture from a semiconductor Si target. Argon and nitrogen were introduced at a constant mass flow rate, whereas oxygen gas was periodically supplied using a rectangular pulsed flow rate. The O₂ injection time T_ON (or duty cycle α) was the only varied parameter. The influences of this parameter on the discharge behaviour, on the Si target voltage, and on the resulting chemical composition of the films were investigated. The temporal evolution of the total pressure exhibits exponential shape differing from the rectangular oxygen pulse shape, due to the response time of the gas flowmeter and to the progressive oxidation of the target and the chamber walls. During the T_ON time, the preferential adsorption of the introduced O₂ induces a decay in Si target voltage. Reversion to the nitrided mode is still possible as soon as the O₂ injection is stopped. The elemental analyses assessed by secondary neutral mass spectrometry (SNMS) showed that the O/N ratio within silicon oxynitride films linearly depends on the T_ON time. Increasing the duty cycle α over a certain value results in an oxidised steady state formation during the T_ON time. This formation was observed by real time measurements of the emission lines ratio I(O^*)/I(Ar^*) indicative of the O₂ partial pressure and confirmed by the time derivative of the target voltage. During the T_OFF time, the alternation with the nitrided mode becomes impossible, leading to the specific synthesis of stoichiometric SiO₂ films.     

Study of structural and electronic environments of hydrogenated amorphous silicon carbonitride (a-SiCN:H) films deposited by hot wire chemical vapor deposition

Hydrogenated amorphous silicon carbon nitride (a-SiCN:H) thin films were deposited by hot wire chemical vapor deposition (HWCVD) using SiH₄, CH₄, NH₃ and H₂ as precursors. The effects of the H₂ dilution on structural and chemical bonding of a-SiCN:H has been investigated by Raman and X-ray photoelectron spectroscopy (XPS). Increasing the H₂ flow rate in the precursor gas more carbon is introduced into the a-SiCN:H network resulting in decrease of silicon content in the film from 41 at.% to 28.8 at.% and sp² carbon cluster increases when H₂ flow rate is increased from 0 to 20 sccm.