Plasma diagnosis and low-substrate-temperature deposition of Ba ferrite films in a damage-free sputtering apparatus with mixed gases

Ba ferrite films have been sputter-deposited from BaO . 6.5(Fe2O3) targets in Ar mixture (Ar of 0.18-0.0 Pa, Xe of 0.0-0.18 Pa and O-2 of 0.02 Pa) and Kr mixture (Kr of 0.18-0.0 Pa, Xe 0.0-0.18 Pa and O-2 0.02 Pa) by using facing targets sputtering apparatus and the plasma characteristics such as the electron density N-e and the electron temperature T-e on the Xe partial pressure P-Xe were evaluated by using Langmuir's probe method. The discharge voltage increased from 490-700 V and 610-680 V for Ar mixture and Kr mixture, respectively with the increase of P-Xe. N-e took minimum value at P-Xe of 0.10 Pa and T-e was almost constant at the neighborhood of the anode ring, while N-e and T-e monotonically increased and decreased with the increase of P-Xe at the center of plasma. Ba ferrite films deposited at P-Xe of 0.10 Pa in Ar mixture, possessed excellent surface smoothness and good magnetic characteristics such as the saturation magnetization 4 pi M-s of 5.1 kG and the anisotropy constant K-u of 4.23 J/m(3). On the other hand, surface smoothness of Ba ferrite films deposited in Kr mixture was not improved and the maximum 4 pi M-s of 4.0 kG was smaller than that of the films deposited in Ar mixture. These results seemed to be caused due to smaller kinetic energy of sputtered atoms at substrate surface. (C) 1998 Elsevier Science Ltd. All rights reserved.