Inductively coupled plasma

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

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Operation

There are two types of ICP geometries: planar and cylindrical. In planar geometry, the electrode is a coil of flat metal wound like a spiral. In cylindrical geometry, it is like a helical spring.

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 currents in the rarefied gas, leading to break down and formation of a plasma. Argon is one example of a commonly used rarefied gas.

Plasma temperatures can range between 6 000 K and 10 000 K, 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 is necessary.

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

Applications

• ICP-AES, a type of atomic emission spectrometry
• ICP-MS, a type of mass spectrometry.
• ICP-RIE, a type of reactive ion etching.

See also

• Pulsed inductive thruster

References