Volume 9 - Dissertation Lisa Wurlitzer
Fortschrittsberichte der Materialforschung und Werkstofftechnik / Bulletin of Materials Research and Engineering
Spectroscopic and Microscopic Studies on the Formation of Silicon Oxide Films from a Two-Stage Plasma Process
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In this dissertation, a novel method for the deposition of silicon oxide films by a PECVD process using silane is considered. The explosive reaction is prevented by a spatial and temporal separation of the reaction gases in a two-step process. In the first process step, a silicon nitride layer is deposited on the substrate by means of a SiH4/N2 gas mixture at room temperature by igniting a dielectrically hindered discharge. This coating is oxidized to SiO2 in the second process step by ignition of oxygen-containing plasma. The subject of this dissertation is the spectroscopic analysis by means of X-ray photoelectron and valence band spectroscopy of the individual process steps as a function of the selected process parameters of partial pressure, treatment time and discharge characteristics. Furthermore, the dependence on the oxygen source for the oxidation and the influence of these parameters on the surface morphology is considered. Finally, based on these investigations, an oxidation mechanism of the deposited silicon nitride layer can be concluded. This is a diffusion-controlled substitution process of nitrogen atoms by oxygen atoms. The rate-determining step is the diffusion of the oxygen atoms through the developing silicon dioxide layer. This process results in a three-layer structure, with the top layer consisting largely of stoichiometric SiO2 with partial intercalation of nitrogen. This is followed by silicon oxynitrides as a transition layer. The lowest layer, which is directly on the substrate, consists of silicon nitride.