Growth and modification of organosilicon films in PECVD and remote afterglow reactors

Five hundred nanometer thick organosilicon coatings are prepared on Si substrates in parallel by the plasma-assisted polymerisation of hexamethyldisiloxane (HMDSO) in an RF-inductively coupled plasma (RFICP) and distributed electron cyclotron resonance plasma (DECRP) at low pressure (0.27 Pa) and of tetramethyldisiloxane (TMDSO) premixed with oxygen in an N-2 microwave induced remote afterglow (MIRA) at 560 Pa. The structure of these different films is analyzed by different techniques, such as Fourier-transform infrared spectroscopy, Rutherford backscattering spectrometry, atomic force microscopy, ellipsometry, and contact angle measurements. Results of the film composition (at least 30% carbon content), optical properties, and morphology indicate a low cross-linking degree accompanied by short chain length for RFICP and DECRP films, in contrast to a high-molecular-weight structure observed for the MIRA film. Carbon removal is achieved within the same plasma reactors by further oxygen-containing plasma treatment per-formed in the RF-ICP (3.33 Pa), DECRP (0.27 Pa, -200 V biased substrate), and MIRA (N-2/O-2 (98.7:1.3, 560 Pa)) reactors. The same measurements are carried out on the treated samples in order to detect the main changes in film composition, optical properties, and morphology. The evolution of surface energy is also studied. The results are discussed according to film structure and process specificity.