MECHANISMS OF PLASMA POLYMERIZATION OF VARIOUS SILICO-ORGANIC MONOMERS

The plasma polymerization of hexamethyl disiloxane (HMDSO), divinyltet ramethyl disiloxane (DVTMDSO), and octamethyl cyclotetrasiloxane (OMCA TS) was investigated using either argon or argon/oxygen mixtures as re actants. With argon, different mechanisms of polymerization for each p olymer were identified reflecting its respective nature. For HMDSO, fo rmation of Si-CH2-Si bonds plays a decisive role, whereas in DVTMDSO S i-(CH2)(4)-Si bridges are formed. In both cases a second mechanism exi sts leading to the loss of SiCxHy groups. Finally, OMCATS polymerizes via the formation of polymethylsiloxane chains and rings. These variou s mechanisms result in differences in the properties of the polymer fi lms. In contrast, almost inorganic films were obtained with oxygen irr espective of the monomer. An investigation of the deposition kinetics shows that the plasma power and the monomer evaporation temperature ar e the decisive parameters determining the polymer growth rates. A comp arison of direct and remote plasma reaction reveals that in the cases of HMDSO and OMCATS direct plasma dissociation is necessary to promote the polymerization process, whereas DVTMDSO also polymerizes under re mote conditions.