Reactive ion etching

Reactive ion etching (RIE) is an etching technology used in microfabrication. It uses chemically reactive plasma to remove material deposited on wafers. The plasma is generated under low pressure (vacuum) by an electromagnetic field. High-energy ions from the plasma attack the wafer surface and react with it. 
A typical (parallel plate) RIE system consists of a cylindrical vacuum chamber, with a wafer platter situated in the bottom portion of the chamber. The wafer platter is electrically isolated from the rest of the chamber, which is usually grounded. Gas enters through small inlets in the top of the chamber, and exits to the vacuum pump system through the bottom. The types and amount of gas used vary depending upon the etch process; for instance, sulfur hexafluoride is commonly used for etching silicon. Gas pressure is typically maintained in a range between a few millitorr and a few hundred millitorr by adjusting gas flow rates and/or adjusting an exhaust orifice. Other types of RIE systems exist, including inductively coupled plasma (ICP) RIE. In this type of system, the plasma is generated with an RF powered magnetic field. Very high plasma densities can be achieved, though etch profiles tend to be more isotropic. A combination of parallel plate and inductively coupled plasma RIE is possible. In this system, the ICP is employed as a high density source of ions which increases the etch rate, whereas a separate RF bias is applied to the substrate (silicon wafer) to create directional electric fields near the substrate to achieve more anisotropic etch profiles.

Further information:

1. Wolf, S.; R.N. Tauber (1986). Silicon Processing for the VLSI Era: Volume 1 - Process Technology. Lattice Press. pp. 531–534
2. Wolf, S.; R.N. Tauber (1986). Silicon Processing for the VLSI Era: Volume 1 - Process Technology. Lattice Press. p. 546
3. Bahadur, Birendra (1990). Liquid Crystals: Applications and Uses. World Scientific. p. 183
4. Walker, Perrin; William H. Tarn (1991). CRC Handbook of Metal Etchants. pp. 287–291
5. Kohler, Michael (1999). Etching in Microsystem Technology. John Wiley & Son Ltd. p. 329
6. В. В. Усова, Т. П. Плотникова, С. А. Кушакевич. Травление титана и его сплавов
7. М. Беккерт, Х. Клемм. Способы металлографического травления. Справочник
8. Article  Reactive ion etching from Wikipedia, the Free Enciclopedia. Available under the license Creative Commons Attribution-Share Alike.

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