Also referred to as physical etching or ion etching (IE). Plasma etching process in which a noble gas is used as process gas. verwendet wird. Since noble gases are atomic gases, there are no radicals in the plasma but only atoms, ions and electrons. There are also no chemical reactions between noble gases and the molecules of the substrate, and thus no chemical etching process. The etching effect occurs because the negatively charged substrate is bombarded with positively charged noble gas ions. To give the substrate its negative charge, it is placed directly on the working electrode, and an RF generator is used for plasma excitation. At this high frequency, only the light and very rapidly moving electrons are accelerated onto the substrate in the phase in which the working electrode is positively charged, but in the opposite case the heavy and too inert ions are not. As a result, the substrate receives a negative charge that is independent of the alternating electromagnetic field. To prevent the substrate from discharging, the working electrode in uncoupled from the generator via a capacitor. The ions are accelerated onto the substrate which now has a static electrically negative charge. Due to their high kinetic energy, substrate atoms, molecules and radicals break out of the surface.
The etching effect is purely anisotropic in the direction of ion bombardment.
The etching rates are low.
The preferred process gas is argon because it is abundant in nature (almost 1% of the atmosphere), correspondingly low-priced, and has a high mass. This gives the impacting ions a high kinetic energy and a high etching effect. The process is comparable to a sandblasting process reduced to nano dimensions. Accordingly, it is also referred to as micro-sandblasting.