Novel facing targets sputtering apparatus with uniform magnetic field and plasma-free substrates

Facing targets sputtering (FTS) systems are known to have excellent charact eristics such as plasma-free substrates and low working gas pressures in th e order of 0.013 Pa. Thus, very smooth and uniform thin films suitable for high-density magnetic recording media can be obtained In this study, the ma gnetic field strength in the plasma necessary to obtain a real plasma- dama ge-free environment around substrates was investigated, focusing on how the magnetic field was distributed in the plasma and thus how the plasma was s ufficiently confined by a magnetic field applied perpendicular to both of t he target planes. For this purpose, an auxiliary magnet was designed for ea ch target and placed at a distance from the main magnet, which was located behind the target The purpose of the auxiliary magnet was to confine and bo ost the magnetic fields generated by the main Al-Ni-Co magnet. An Fe-Nd-B m agnet was used for the auxiliary magnet, because it was mechanically thin a nd had strong magnetic characteristics. To evaluate the plasma density dist ribution, the distribution of the electric potential was measured with a pr obe. The substrate voltage was also measured with a voltmeter to confirm th at the environment around the substrates was plasma-free. One result of the design was that the electric potential distribution had much better unifor mity than before (from -6 to -2 V); another was that the substrate voltage was slightly positive, indicating that the substrates were plasma-free. An FTS system with the above features is currently being used in various engin eering experiments to fabricate plasma- damage-free thin films that ha ve e xcellent magnetic and recording characteristics for magnetic recording medi a. (C) 1998 Elsevier Science Ltd. All rights reserved.