Characterization of diffused ECR plasma - Application to pulsed plasma ion implantation of nitrogen in titanium

A compact surface electron cyclotron resonance (ECR) plasma source, developed at Institut National de la Recherche Scientifique (INRS)-Energie et Materiaux, has been used as a versatile surface treatment tool, The source has been operated with nitrogen for application to plasma assisted nitriding near room temperature. A negatively biased titanium target is immersed in the processing chamber (PC) plasma. The pulsed plasma diffuses from the ECR source across a transparent grid and fills the PC. The ions are accelerated and implanted into the Ti target. The electric field distribution in the PC, and therefore the uniformity of the implantation, was controlled using a highly transparent grounded grid. For a typical operating pressure of about 0.1-0.2 Pa, and with similar to 300 W of microwave power coupled to the plasma source, a flat density profile with n(c) = 2.5 x 10(15) m(-3) (over a diameter > 0.07 m) was measured by a scanning Langmuir probe in the PC. The electron temperature was 6.5 eV, and it also had a Aat profile. In these preliminary experiments, ion nitriding of titanium samples was achieved with 30 keV nitrogen ion implantation. The hardness of the Ti target surface changed from 3.4 GPa to 5.8 GPa following the implantation. The depth profile of the implanted ions, measured by the X-ray photoelectron spectroscopy technique, combined with the simulation results from the TRIM code suggests that ion-neutral collisions in the PC were not frequent enough to alter the ion energy distribution significantly. (C) 1998 Elsevier Science S.A.