Study of plasma mechanisms of hybrid a-SiOC:H low-k film deposition from decamethylcyclopentasiloxane and cyclohexene oxide

The deposition of hybrid a-SiOC:H dielectric films from decamethylcyclopentasiloxane/cyclohexene oxide/helium (D5/CHO/He) plasmas has been investigated in various operating conditions. In order to understand the influence of molecule fragmentation on the film formation, the species in the plasma were monitored by optical emission spectroscopy and mass spectroscopy. The films were analyzed with spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The CHO molecule loss rate under fragmentation and film formation was always much higher than that of D5, with the ratio depending on the plasma conditions. The CHO was found to lose at least CO, CH, H and C3 groups whereas D5 main reactions in plasma occurred through Si-CH3 and C-H bond dissociation, leaving its cyclic structure unaltered. This suggested that different hydrocarbon fragments got incorporated in the film thanks to the presence of CHO in the gas feed compared to D5 alone deposited films. Moreover some Si-O-Si structure indicated a high level of the D5 cycle preservation in the film. The deposition rate increased linearly with RF plasma power for D5 films and for D5/CHO films. It was enhanced by the presence of CHO in the plasma.