Plasma processing and chemistry*
Daniel C. Schram
Eindhoven University of Technology, Department of Physics,
P.O. Box 513, 5600 MB Eindhoven, The Netherlands
Abstract: Plasma deposition and plasma conversion can be characterized
by five steps: production by ionization, transfer of chemistry to precursors,
transport of radicals to the surface, surface interactions with deposition,
recirculation and generation of new monomers. For very fast deposition,
large flows of radicals are needed and a regime is reached, in which
monolayer coverage is reached in a very short time. Such large flows
of radicals can be obtained by ion-induced interactions, as the C2H
radical from acetylene for a-C:H deposition, or by H atom abstraction
as the SiH3 radical from SiH4 for a-Si:H deposition. These radicals
with intermediate sticking coefficient are advantageous as they are
mobile and have a finite dwelling time at the surface. By such a pure
radical mechanism, good layers can be formed with very high growth rates,
if large radical fluxes can be reached. This regime of high fluence
is also interesting for conversion, of which ammonia formation from
hydrogen and nitrogen atoms is given as an example. These new approaches
offer new possibilities for further development of the field in close
connection with surface science, catalysis, and materials science.
* Lecture presented at the 15th International Symposium
on Plasma Chemistry, Orléans, France, 9-13 July 2001. Other presentations
are presented in this issue, pp. 317–492.
** Corresponding author.
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