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Carbon doped oxide dielectrics comprised of Si, C, O, and H (SiCOH) have been
prepared by plasma enhanced chemical vapor deposition (PECVD) from mixtures of
tetramethylcyclotetrasiloxane (TMCTS) and an organic precursor. The films have been
analyzed by determining their elemental composition and by Fourier transform infrared
spectroscopy (FTIR) with deconvolution of the absorption peaks. The analysis has shown that PECVD of TMCTS produces a highly-crosslinked networked SiCOH film.
Dissociation of TMCTS appears to dominate the deposition chemistry as evidenced by
the multitude of bonding environments and formation of linear chains and branches.
Extensive crosslinking of TMCTS rings occurs through Si-Si, Si-CH2-Si, Si-O-Si, and Si-CH2-O-Si moieties.
The films deposited from mixtures of TMCTS and organic precursor incorporate
hydrocarbon fragments into the films. This incorporation occurs most probably through
the reaction of the organic precursor and the Si-H bonds of TMCTS. Annealing the
SiCOH films deposited from TMCTS and organic precursor results in a large loss of
carbon and hydrogen from the films resulting from the fragmentation and loss of the
incorporated organic component. The deconvolution of the Si-O-Si asymmetric stretching band of the annealed films shows the existence of a larger fraction of a cage structure and a correspondingly smaller fraction of a networked (highly crosslinked) structure in the SiCOH films deposited from mixtures of TMCTS with organic precursor relative to the films deposited from TMCTS only. The evolution of the volatile hydrocarbon fragments during annealing results in the formation of nanopores and subsequent reduction of the dielectric constants of the films to extreme low-k values.

By: Alfred Grill, Deborah Neumayer

Published in: Journal of Applied Physics, volume 94, (no 10), pages 6697-707 in 2003


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