OES and FTIR diagnostics of HMDSO/O2 gas mixtures for SiOx deposition assisted by RF plasma

A capacitively coupled radiofrequency PACVD process for SiOx deposition using oxygen-hexamethyldisiloxane (HMDSO) gas mixtures is characterised under a pressure of 1 Torr. Optical emission spectroscopy and FTIR absorption spectroscopy analyses are performed for different values of the dilution ratio Xhm of HMDSO in oxygen. The power delivered to the plasma is set high enough (5 W/cm2) to have a strong fragmentation of the monomer by electron impact. Two different regimes are then observed depending whether Xhm exceeds or not 20 vol.%. Below this critical value, the monomer fragments are strongly oxidised. Above, densities of CO and CH4 molecules strongly decrease. Trends observed in the evolution of the species concentrations as a function of Xhm better agree the results by Aumaille et al. [K. Aumaille, C. Vallée, A. Granier, A. Goullet, F. Gaboriau, G. Turban, Thin Solid Films 359 (2000) 188] than those by Lamendola et al. [R. Lamendola, R. d’Agostino, F. Fracassi, Plasmas Polym. 2 (1997) 147] despite the pressure set in this work is closer to that used by the latter.