Hot-filament chemical vapor deposition of organosilicon thin films from hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane

A nonplasma technique, hot-filament chemical vapor deposition (HFCVD), is an alternative method for producing organosilicon films of novel structure. Films are deposited onto room-temperature substrates from the precursors hexamethylcyclotrisiloxane (D-3) and octamethylcyclotetrasiloxane (D-4) at high rates (>1 mum/min). Filament temperature can be used to control film structure, and the limited reaction pathways available via thermal decomposition make it possible to elucidate the chemistry of the growth process. During film growth, there appears to be competition between reaction pathways for the incorporation of cyclic and linear siloxane structures. For both D-3 and D-4 HFCVD films, infrared, Raman, and nuclear magnetic resonance spectroscopies indicate the incorporation of ring structures consisting of three siloxane units. The concentration of these structures increases as filament temperature is raised and is especially pronounced for films deposited from D-3. In comparison, films grown from D-4 show a greater degree of incorporation of linear, unstrained structures over the range of filament temperatures studied. In contrast to plasma-deposited organosilicon films, cross-linking in HFCVD films occurs predominantly via silicon-silicon bonding and not from siloxane bonds with tertiary or quaternary silicon atoms. (C) 2001 The Electrochemical Society.