ABSTRACT
In dry etching, substrates are etched without wet chemicals or rinsing and enter and leave the etching system in a dry state. The term dry etching covers a family of methods by which a solid surface is etched in the gas or vapor phase physically by ion bombardment,
chemically by a chemical reaction through a reactive species at the surface, or by combined physical and chemical mechanisms or reactive ion etching (RIE). A key ingredient in dry etching involves the creation of plasma. Plasma-assisted dry etching is categorized according to the specific setup as either glow discharge etching (diode setup) or ion-beam etching (triode setup). Using glow discharge techniques, a broad plasma is generated in the same part of the vacuum chamber where the substrate is located; when using ion-beam techniques, plasma is generated in a separate chamber or in another part of the same vacuum chamber from which ions are extracted and directed in a beam toward the substrate by a number of electrode grids. In Figure 3.2 we compare a dry etching diode and dry etching triode setup.1 It is also common to differentiate between 1) physical sputter/ion etching and ion-beam etching (IBE)2 or also ion-beam milling (IBM), 2) chemical plasma etching (PE), and 3) synergetic reactive ion etching (RIE). Each of these techniques will be discussed in detail further below, but here we present a short dry etching synopsis:
1. In physical sputter/ion etching and ion-beam milling (IBE), etching occurs as a consequence of a purely physical effect, namely, momentum transfer between energetic Ar+ ions and the substrate surface. Some type of chemical reaction takes place in all the other dry etching methods, but not in this one.
