Area selective atmospheric pressure PECVD of organosilicon precursors: Role of vinyl and ethoxy groups on silicon oxycarbide deposition patterns - A case study

An atmospheric pressure Dielectric Barrier Discharge plasma torch was used to perform selective area plasma enhanced chemical vapour deposition of four organosilicon precurors: Triethylvinylsilane (VTES), Vinyltriethoxysilane (VTEOS), Tetraethoxysilane (TEOS) and Tetraethylsilane (TES). The precursors were chosen in such a way that they differ only by the presence or absence of vinyl and/or ethoxy groups. Experimentally, major differences have been observed on the deposition speed, coating patterns and thin film composition. Precursor with vinyl group has confined deposition at the central region of plasma torch, in contrast precursor with only ethoxy groups has circular deposition in the periphery region of plasma torch, and precursors with both the vinyl and ethoxy groups has deposition at both locations. A detailed chemical analysis revealed the film composition to be silicon oxycarbide (SiOxCyH) with high content of carbon for the central region's coating whereas the peripherical coating is close to silica like (SiOx) with a minuscule carbon content. Coatings patterns and composition have been investigated in the light of gaseous flows mixing obtained from computational Fluid Dynamic (CFD) simulation. A strong correlation is evidenced for central SiOxCyH deposition of vinyl containing precursors, to the high concentration of precursor. Whereas the peripheral SiOx deposition of ethoxy containing precursors corresponds to high concentration of plasma species. Furthermore, the role of reactive plasma species on the underlying deposition mechanisms has been identified as crucial and has been purposed as the driving factor.