New trends in DECR plasma technology: applications to novel duplex treatments and process combinations with extreme plasma specifications

After a brief review of the plasma production and diffusion mechanisms above multipolar magnetic field structures, the possible means of sustaining magnetron discharges are listed. In particular, various designs of distributed electron cyclotron resonance (DECR) plasma reactors are described. At the industrial level, besides gas and pumping distribution, the control of plasma uniformity (up to square meters) is a necessary condition to obtain the desired uniformity of reactive species. Another process parameter, controlled via independent substrate biasing, is the energy distribution function of ions onto surfaces. Plasma-based ion implantation (PBII) in the 100-keV range requires large volumes (cubic meters) of very low-pressure plasma (below 10−4 torr), whereas ion bombardment in the very low energy range (a few eV) can only be obtained with quiescent, magnetic field-free plasmas exhibiting a very low electron temperature. In contrast, increasing the electron temperature of the diffusion plasma can enhance ionization of metallic vapors present in the central volume of a DECR reactor. The control of plasma parameters in magnetron-like plasmas opens new possibilities for complex treatments associating successive processes with extreme plasma specifications. As examples, thermochemical processing at low ion bombardment energy can be performed in DECR plasmas. Results on plasma nitriding of stainless steel for industrial applications are reported. More generally, plasma-assisted deposition (PAD) or PBII and deposition (PBIID), using chemical (CVD) or physical vapor deposition (PVD), can be operated with magnetron-like discharges: PACVD and PBIICVD in DECR plasmas, PAPVD and PBIIPVD in hybrid DECR magnetron reactors.