Plasma parameters of pulsed-dc discharges in methane used to deposit diamondlike carbon films

Corbella, C.; Rubio-Roy, M.; Bertran, E.; Andújar, J. L.

doi:doi:10.1063/1.3183945

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Control of plasma uniformity in a capacitive discharge using two very high frequency power sources

Very high frequency (VHF) capacitively coupled plasma (CCP) discharges are being employed for dielectric etching due to VHF’s various benefits including low plasma potential, high electron density, and controllable dissociation. If the plasma is generated using multiple VHF sources, one can expect that the interaction between the sources can be important in determining the plasma characteristics. The effects of VHF mixing on plasma characteristics, especially its spatial profile, are investigat...

Effect of radio frequency discharge power on dusty plasma parameters

The parameters of a two-dimensional dusty plasma consisting of six, 9 μm diameter particles trapped inside a radio frequency (rf) plasma sheath have been measured as a function of rf power in a 13.5 mtorr (1.8 Pa) argon discharge. The center-of-mass and breathing frequencies are found by projecting the cluster’s Brownian motion onto the associated normal mode. The center-of-mass frequency (i.e., radial confinement) is insensitive to rf power. The Debye shielding parameter κ, as found from the b...

Here we approximate the plasma kinetics responsible for diamondlike carbon (DLC) depositions that result from pulsed-dc discharges. The DLC films were deposited at room temperature by plasma-enhanced chemical vapor deposition (PECVD) in a methane (CH₄) atmosphere at 10 Pa. We compared the plasma characteristics of asymmetric bipolar pulsed-dc discharges at 100 kHz to those produced by a radio frequency (rf) source. The electrical discharges were monitored by a computer-controlled Langmuir probe operating in time-resolved mode. The acquisition system provided the intensity-voltage (I-V) characteristics with a time resolution of 1 μs. This facilitated the discussion of the variation in plasma parameters within a pulse cycle as a function of the pulse waveform and the peak voltage. The electron distribution was clearly divided into high- and low-energy Maxwellian populations of electrons (a bi-Maxwellian population) at the beginning of the negative voltage region of the pulse. We ascribe this to intense stochastic heating due to the rapid advancing of the sheath edge. The hot population had an electron temperature Tehot of over 10 eV and an initial low density nehot which decreased to zero. Cold electrons of temperature Tecold ∼ 1 eV represented the majority of each discharge. The density of cold electrons necold showed a monotonic increase over time within the negative pulse, peaking at almost 7×10¹⁰ cm⁻³, corresponding to the cooling of the hot electrons. The plasma potential V_p of ∼ 30 V underwent a smooth increase during the pulse and fell at the end of the negative region. Different rates of CH₄ conversion were calculated from the DLC deposition rate. These were explained in terms of the specific activation energy E_a and the conversion factor x_dep associated with the plasma processes. The work deepens our understanding of the advantages of using pulsed power supplies for the PECVD of hard metallic and protective coatings for industrial applications (optics, biomedicine, and electronics).

Article Outline

INTRODUCTION
EXPERIMENTAL SETUP
1. Reactor description and operating conditions
2. Data acquisition
RESULTS AND DISCUSSION
1. Analysis of the I-V characteristics
  1. Modeling
  2. Calculation of the plasma parameters
2. rf discharges monitored by a Langmuir probe
  1. I-V characteristics
  2. Plasma parameters
3. Bipolar pulsed-dc discharges monitored by a fast Langmuir probe
  1. Time-resolved recording of I-V characteristics
  2. Tracking plasma parameters
    1. Electron temperature
    2. Plasma density
    3. Plasma and floating potentials
  3. Averaged parameters
4. Input power and deposition rate
  1. Growth regimes
  2. Power dissipation modes
CONCLUSIONS

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KEYWORDS and PACS

Keywords

diamond-like carbon, discharges (electric), electron density, hot carriers, Langmuir probes, plasma boundary layers, plasma CVD coatings, plasma density, plasma sheaths, plasma temperature, protective coatings, thin films

PACS

52.77.Dq

Plasma-based ion implantation and deposition
81.15.Gh

Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Fq

High-field and nonlinear effects
52.80.-s

Electric discharges
52.70.Ds

Electric and magnetic measurements
68.55.aj

Insulators

ARTICLE DATA

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http://link.aip.org/link/doi/10.1063/1.3183945

PUBLICATION DATA

ISSN:

0021-8979 (print)

1089-7550 (online)

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American Institute of Physics

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