Preparation of Co and CoNx thin films by unbalanced radio frequency magnetron sputtering

Abstract

We have developed a modified process based on an unbalanced magnetron sputtering of a magnetic Co target (100 mm φ, 5 mm thick) to deposit Co and CoNx films. The plasma confinement can be controlled by the shape of the magnetic field in the sputter deposition device with a multipolar magnetic-field plasma confinement. Cobalt films were prepared by this sputtering system at the radio frequency powers of 100–200 W and argon pressure down to 8.0×10−2 Pa. It is shown that the deposition rate of Co films significantly increases from 8.7 to 25 nm/min whose values are two times that of a conventional magnetron sputtering. A Co film with the orientation of (111) plane is formed and the value of the grain size estimated from the plane is about 30 nm. Cobalt nitride (CoNx) films were also prepared by unbalanced magnetron sputtering in a plasma of an argon and nitrogen gas mixture. It is also found from the results of electron probe microanalysis that the content of nitrogen in CoNx films increases with the increasing gas flow ratio of N2. The electrical resistivity for reactively sputtered films is less than 80 μΩ cm, which makes this compound a relatively good conductor.