Inductively coupled plasma

Fig. 1. Picture of an analytical ICP torch

An inductively coupled plasma (ICP) or transformer coupled plasma (TCP)[1] is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.[2]

Operation

There are three types of ICP geometries: planar (Fig. 2 (a)), cylindrical [3] (Fig. 2 (b)), and half-toroidal (Fig. 2 (c)).[4]

Fig. 2. Conventional Plasma Inductors

In planar geometry, the electrode is a length of flat metal wound like a spiral (or coil). In cylindrical geometry, it is like a helical spring. In half-toroidal geometry, it is toroidal solenoid cut along its main diameter to two equal halves.

When a time-varying electric current is passed through the coil, it creates a time-varying magnetic field around it, which in turn induces azimuthal electric field in the rarefied gas, leading to the formation of the figure-8 electron trajectories[4] providing a plasma generation (see Hamilton-Jacobi equation in electromagnetic fields). Argon is one example of a commonly used rarefied gas.

Applications

Plasma electron temperatures can range between ~6 000 K and ~10 000 K (~6 eV - ~100 eV),[4] comparable to the surface of the sun. ICP discharges are of relatively high electron density, on the order of 1015 cm−3. As a result, ICP discharges have wide applications where a high-density plasma (HDP) is needed.

Another benefit of ICP discharges is that they are relatively free of contamination because the electrodes are completely outside the reaction chamber. By contrast, in a capacitively coupled plasma (CCP), the electrodes are often placed inside the reactor and are thus exposed to the plasma and subsequent reactive chemical species.

See also

References

  1. High density fluorocarbon etching of silicon in an inductively coupled plasma: Mechanism of etching through a thick steady state fluorocarbon layer T. E. F. M. Standaert, M. Schaepkens, N. R. Rueger, P. G. M. Sebel, and G. S. Oehrleinc
  2. A. Montaser and D. W. Golightly, eds. (1992). Inductively Coupled Plasmas in Analytical Atomic Spectrometry. VCH Publishers, Inc., New York,.
  3. Pascal Chambert and Nicholas Braithwaite (2011). "Physics of Radio-Frequency Plasmas". Cambridge University Press, Cambridge: 219–259. ISBN 978-0521-76300-4.
  4. 1 2 3 Shun'ko, Evgeny V.; Stevenson, David E.; Belkin, Veniamin S. (2014). "Inductively Coupling Plasma Reactor With Plasma Electron Energy Controllable in the Range From ~6 to ~100 eV". IEEE Transactions on Plasma Science. 42 (3): 774–785. Bibcode:2014ITPS...42..774S. doi:10.1109/TPS.2014.2299954. ISSN 0093-3813.
  5. Ben Ohayon, Erik Wahlin and Guy Ron (2015). "Characterization of a metastable neon beam extracted from a commercial RF ion source". 10 (03). Journal of Instrumentation, Cambridge: P03009. arXiv:1502.05376Freely accessible. Bibcode:2015JInst..10P3009O. doi:10.1088/1748-0221/10/03/P03009.
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