AVS 49th International Symposium
    Plasma Science Thursday Sessions
       Session PS+TF-ThM

Paper PS+TF-ThM11
Detailed Study of Chemistry of Ar/C@sub 2@H@sub 2@ Plasma and Consequences For the a-C:H Film Growth

Thursday, November 7, 2002, 11:40 am, Room C-103

Session: Plasma Enhanced Deposition
Presenter: M.C.M. Van de Sanden, Eindhoven University of Technology, The Netherlands
Authors: J. Benedikt, Eindhoven University of Technology, The Netherlands
R.V. Woen, Eindhoven University of Technology, The Netherlands
M.C.M. Van de Sanden, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The role of hydrocarbon radicals during the deposition of a-C:H films is studied in an Ar/C@sub 2@H@sub 2@ remote expanding thermal plasma (ETP) reactor. C, C@sub 2@ and CH radicals are detected by means of cavity ring down spectroscopy (CRDS) at different plasma conditions and at different positions downstream from the thermal plasma source. A broadband absorption (BBA) is observed in the 250 - 520 nm region. Acetylene and diacetylene (C@sub 4@H@sub 2@) are monitored with a residual gas analyser. A simple plasma chemistry model is developed to explain measured data. The plasma chemistry is governed by argon ion induced dissociation of acetylene molecules. Main product of this reaction is the ethynyl (C@sub 2@H) radical, which can further react either with argon ions or with acetylene, depending on the ratio between the flux of argon ions and the flux of acetylene into the reactor. The BBA is due at least two species: most likely candidates are C@sub 2@H radical and C@sub 4@H@sub 2@ molecule. In-situ real-time ellipsometry was used to determine growth rate and refractive index of the films grown. Our preliminary conclusion is that C@sub 2@H radical is a growth precursor for high quality hard diamond-like a-C:H films; a-C:H films with slightly lower hardness but faster growth rate were also deposited using a C@sub 4@H@sub 2@ rich plasma. The loss probabilities of the ethynyl radical and diacetylene molecule are determined from time dependent CRDS. The probabilities can be used to monitor the relative importance of the ethynyl radical vs. diacetylene in the growth of a-C:H.