Improvement of toroidal plasma (TP) type sputtering for depositing Co-Cr films on plasma-free substrates

Co-Cr films for perpendicular recording have been deposited by toroidal plasma (TP) sputtering method. A magnetic field was applied by a solenoid coil or a magnet was attached to the outer pole to change the plasma state during sputtering. When the magnetic field was applied using the solenoid coil, the discharge current, film thickness and film composition, saturation magnetization of 480~800 emu/cm³, and coercivity of 250~350 Oe in the films depended on the plasma state. On the other hand, by attaching the magnet to the outer pole, the magnetic flux distribution in front of the target plane was significantly improved. Therefore, the applied voltage to the electrodes was reduced from 520 to 440 V at an Ar gas pressure of 0.2 Pa. The erosion profile of the targets was changed, and variations in the film thickness and the Co content over the whole film plane were reduced