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What Is Reactive Ion Etching?

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  • Written By: Donn Saylor
  • Edited By: John Allen
  • Last Modified Date: 24 March 2014
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    Conjecture Corporation
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Reactive ion etching is a type of technology used in microfabrication to remove substances from wafers. Wafers are small semiconductor strips used in the creation of microdevices, and reactive ion etching technology ensures they remain free of materials that could negatively impact their efficacy. Microfabrication procedures are performed with specially designed devices that pinpoint the substance to be removed without sacrificing the integrity of the wafer.

The most common reactive ion etching device is made of a cylinder-shaped vacuum compartment with an isolated holder for the wafer attached to the bottom part of the chamber. There are small holes in the top of the vessel that let in gas. Various types of gases are used, depending on the individual requirements of a particular wafer.

Inductively coupled plasma is another mode of this technology. With this device, the plasma is crafted by a highly specialized magnetic field. It is not uncommon to attain high levels of plasma concentration with this method.

Reactive ion etching plasma is a state of matter that is chemically reactive and is created by the more standard radio frequency (RF) electromagnetic field. Ions within the plasma have an unusually high amount of energy. These ions react to the debris on a wafer and work to remove the defects on its surface.

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The chemical process involved in reactive ion etching is a multi-faceted one. First, a substantial electromagnetic field is sent to the wafer chamber. The field then oscillates, which ionizes the molecules of gas in the vessel and removes their electrons. This results in the creation of the plasma.

Reactive ion etching is one type of a broader category of microfabrication removal called dry etching. It uses no liquids in the removal process, unlike wet etching, which uses various acids and chemicals to achieve the same end. Since wet etching causes undercutting to the wafer, as well as significant amounts of toxic waste, dry etching is becoming a more popular method of wafer chemical removal.

One of the major drawbacks of reactive ion etching is cost. Compared to wet etching techniques, it is much more expensive due to the specialized equipment needed. Dry etching processes in general are far more effective in reaching trickier areas of a wafer, however. It is important to remember, though, that some jobs do not require the minute detail provided by this form of etching, and wet etching procedures may accomplish the task just as effectively.

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