Etching of iron and iron-chromium alloys using ICP-RIE chlorine plasma

Dry etching process of iron, chromium and iron-chromium alloys under a chlorine-based plasma is studied. The objective is to create new surface functionalities. Our approach is twofold: on the one hand, an experimental study in an ICP (Inductively Coupled Plasma) reactor and, on the other hand, the development of an etching model based on a multi-scale approach including kinetic, sheath and surface models. Results from plasma etching of substrates in Fe, Cr and in Fe-Cr alloys are presented. Optical emission spectroscopy and interferometry measurements show strong modifications of the plasma when Fe or Cr samples are present in the reactor. It is shown that iron is easier to etch than chromium. Our study highlights the role of chemical etching by the formation of volatile products such as FeCl3. The chromium content in Fe-Cr alloys has a strong impact on both the lateral and vertical etch rates, as well as on the roughness along the profile. For Fe-Cr alloys, the etch rates measured experimentally and estimated numerically are very similar. In order to make the results from our model in accordance with the experimental ones, the concept of hard zones was introduced. This final agreement between simulation and experience shows the capability of our developed simulator to implement new phenomenas.