No abstract

The dry etching process of Fe, Cr and Fe-Cr alloys under a chlorine-based plasma is studied. The objective is to create new surface functionalities. The approach combines an experimental study of an ICP (Inductively Coupled Plasma) reactor with the development of a multi-scale etching model including kinetic, sheath and surface models. The results from plasma etching of substrates made of Fe, Cr and 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 Fe is easier to etch than Cr. The study highlights the role of chemical etching by the formation of volatile products such as FeCl 3 . The Cr 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 experimental and calculated values of etch rate are very similar. The concept of hard zones is introduced to get a better agreement between simulation results and experimental ones. This good agreement demonstrates the capability of the developed simulator to implement new phenomena.

In this paper, we present the results of plasma nitriding treatments on austenitic stainless steel substrates previously coated with a patterned silicon oxide layer. For this purpose, masks were made by PECVD for the deposition of a silicon oxide layer on polished austenitic AISI 316L samples. For the final nitriding treatment, we used a multi-dipolar plasma providing independent substrate polarization. The interactions between expanded austenite and fixed silicon oxide mask in different shapes (circular and square dots) are observed by atomic force microscopy (AFM) on the same area before and after the nitriding treatment. After this thermochemical treatment, we obtain strong distortions of the dots, in particular at the edges of the larger size dots. The role of elastic deformation, due to the expanded austenitic phase formed by the diffusion of nitrogen under the mask is of primary importance.