An innovative GC-MS, NMR and ESR combined, gas-phase investigation during chemical vapor deposition of silicon oxynitrides films from tris(dimethylsilyl)amine

Abstract

Tris(dimethylsilyl)amine (TDMSA) is used in the presence of O₂ and NH₃ for the atmospheric pressure chemical vapor deposition (CVD) of conformal, corrosion barrier silicon oxynitride (SiO_xN_y) films at moderate temperature. Plausible decomposition pathways taking place during the process, as well as resulting gas-phase by-products, are investigated by an innovative methodology, coupling solid-state films characteristics with gas phase analysis. Liquid NMR, gas chromatography coupled with mass spectrometry (GC-MS) and electron spin resonance (ESR) allow probing stable compounds and radical intermediate species in the gas phase. At least fifteen by-products are identified, including silanols, siloxanes, disilazanes, silanamines, and mixed siloxane–silanamine molecules, in addition to more usual compounds such as water. The radical dimethylsilane, Me₂HSi˙, is noted across all experiments, hinting at the decomposition of the TDMSA precursor. Deposition of SiO_xN_y films occurs even in the absence of NH₃, demonstrating the judicious choice of the silanamine TDMSA as a dual source of nitrogen and silicon. Additionally, the presence of Si–H bonds in the precursor structure allows formation of SiO_xN_y films at temperatures lower than those required by other conventional silazane/silanamine precursors. Addition of NH₃ in the inlet gas supply results in lower carbon impurities in the films. The identified by-products and formulated decomposition and gas-phase reactions provide stimulating insight and understanding of the deposition mechanism of SiO_xN_y films by CVD, offering possibilities for the investigation of representative chemical models and process simulation.