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

A nonplasma technique, hot-filament chemical vapor deposition (HFCVD), is a n alternative method for producing organosilicon films of novel structure. Films are deposited onto room-temperature substrates from the precursors he xamethylcyclotrisiloxane (D-3) and octamethylcyclotetrasiloxane (D-4) at hi gh rates (>1 mum/min). Filament temperature can be used to control film str ucture, and the limited reaction pathways available via thermal decompositi on make it possible to elucidate the chemistry of the growth process. Durin g film growth, there appears to be competition between reaction pathways fo r the incorporation of cyclic and linear siloxane structures. For both D-3 and D-4 HFCVD films, infrared, Raman, and nuclear magnetic resonance spectr oscopies 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 fro m D-3. In comparison, films grown from D-4 show a greater degree of incorpo ration of linear, unstrained structures over the range of filament temperat ures studied. In contrast to plasma-deposited organosilicon films, cross-li nking in HFCVD films occurs predominantly via silicon-silicon bonding and n ot from siloxane bonds with tertiary or quaternary silicon atoms. (C) 2001 The Electrochemical Society.