Microstructure of high-purity Fe films deposited by the non-mass-separated ion beam deposition method

High purity Fe films were uniformly deposited on 2-inch Si wafers at room temperature by using a newly developed non-mass-separated ion beam deposition (IBD) system. Fe+ ion production was performed in an r.f.-sputter type ion source with a high purity (99.999%) Fe rod target. Shiny metallic surfaces were obtained for all the deposited Fe films and no distinct corrosion pits were found even after 6 months' air exposure. SIMS analysis of the Fe films indicated that the purity was much improved compared with that of the Fe films which were previously deposited by the mass-separated IBD method. However, the electrochemical measurement in 0.001 M NaCl solution showed that the corrosion current density for the non-mass-separated IBD-Fe films was almost two orders larger than that of the mass-separated IBD-Fe films deposited at 50 eV. High resolution SEM and thin film XRD observations indicated that the Fe films were of columnar structure with a (110) preferred orientation, whereas our previous mass-separated LED Fe films gave us a non-columnar structure. This difference in microstructure seems to be a reason for the higher corrosion current density. (C) 1998 Elsevier Science S.A. All rights reserved.