Influence of the process parameters on the properties of hydrogenated amorphous carbon thin films deposited using ECR plasma


Influence of the process parameters on the properties of hydrogenated amorphous carbon thin films deposited using ECR plasma

Piazza, F.; Arnal, Y.; Grambole, D.; Herrmann, F.; Kildemo, M.; Lacoste, A.; Relihan, G.; Golanski, A.

A uniformly distributed multipolar microwave plasma reactor using electron cyclotron resonance at 2.45 GHz (600 W) was used to deposit a-C:H thin films at RT. C2H2 was used as precursor gas. Single crystal <100> Si and CR39 allelic resin substrates were RF biased to a negative voltage within the range between -10 and -200 V. The influence of the process parameters (gas flow and substrate bias) on the growth rate and hydrogen content have been investigated in detail. Optical parameters (optical gap ET, index of refraction n and extinction coefficient k) were measured using spectroscopic ellipsometry. The resonant (6.385 MeV) nuclear reaction: 1H(15N, alpha gamma)12C was used to determine the hydrogen content. For the C2H2 pressure range of 0.6 < P( C2H2) < 1.1 mTorr the optical parameters remain constant within the limits of experimental uncertainty. The sp3 content is seen to vary monotonically as a function of pressure and to be reaching a maximum of about 40% for 0.6 < P( C2H2) < 0.7 mTorr. The variation of the substrate bias within the range from -10 V to -190 V (at P( C2H2) = 0.6 mTorr) has no measurable impact neither on the deposition rate nor on the hydrogen content. The corresponding average values of ET and n remain stable (ET = 1.83 ± 0.11 eV, n = 2.12 ± 0.04). However, an increase in the bias is followed by a significant decrease of the extinction coefficient k and of the absorption tail width E0 . The observed evolution of k and E0 suggests that the sp2 clustering mode may be related to the substrate bias.

Keywords: carbon; thin films; hard coatings; optical properties; plasma processing

  • Poster
    EMRS'2000, 30. May - 2. June 2000, Strasbourg, France
  • Thin Solid Films 383(2001), 196-199

Permalink: https://www.hzdr.de/publications/Publ-3739
Publ.-Id: 3739