The RIE process (Reactive Ion Etching) is a dry etching process which is mainly used in electronics and microelectronics production for rapid surface cleaning or activation, for ashing photoresist or for structuring circuits on semiconductor wafers.

A so-called planar plate reactor is generally used for this purpose, as shown schematically in Figure 1. If a high-frequency alternating voltage is applied to the electrodes at a negative pressure in the range of 10-2 to 10-1 mbar, a low-pressure gas discharge (plasma) is ignited. Due to the different mobility of the charged gas particles in the plasma (heavy ions, light electrons), a negative potential builds up at the smaller electrode, the so-called self-bias potential. This is in the range of a few 10 to a few 100 volts.

Two effects now take place on substrates (wafers, printed circuit boards, etc.) which lie on the smaller electrode when the correct process gases are used:

1. Chemical removal of the substrate surface or existing impurities through the reaction with reactive particles from the plasma (plasma etching)
2. Physical removal by direct momentum transfer of ions accelerated in the electric field to the surface (sputter etching)

The RIE process combines the advantages of both effects - high selectivity, high etching rate and anisotropic removal.