Enhanced tunability of the composition in silicon oxynitride thin films by the reactive gas pulsing process

Silicon oxynitride thin films were sputter deposited by the reactive gas pulsing process. Pure silicon target was sputtered in Ar, N-2 and O-2 mixture atmosphere. Oxygen gas was periodically and solely introduced using exponential signals. In order to vary the injected O-2 quantity in the deposition chamber during one pulse at constant injection time (T-ON), the tau mounting time tau(mou) of the exponential signals was systematically changed for each deposition. Taking into account the real-time measurements of the discharge voltage and the I(O*)/I(Ar*) emission lines ratio, it is shown that the oscillations of the discharge voltage during the T-ON and T-OFF times (injection of O-2 stopped) are attributed to the preferential adsorption of the oxygen compared to that of the nitrogen. The sputtering mode alternates from a fully nitrided mode (T-OFF time) to a mixed mode (nitrided and oxidized mode) during the T-ON time. For the highest injected O-2 quantities, the mixed mode tends toward a fully oxidized mode due to an increase of the trapped oxygen on the target. The oxygen (nitrogen) concentration in the SiOxNy films similarly (inversely) varies as the oxygen is trapped. Moreover, measurements of the contamination speed of the Si target surface are connected to different behaviors of the process. At low injected O-2 quantities, the nitrided mode predominates over the oxidized one during the T-ON time. It leads to the formation of Si3N4-yOy-like films. Inversely, the mixed mode takes place for high injected O-2 quantities and the oxidized mode prevails against the nitrided one producing SiO2-xNx-like films. Published by Elsevier B.V.