Plasma properties of a new surface-wave-sustained plasma source under the conditions of depositing DLC films

Abstract

Surface-wave-sustained plasma (SWP) is a low-pressure, high-density plasma. Applying this technique, it is promising to prepare hydrogen-free diamond-like carbon (DLC) films with excellent characteristics by physical vapor deposition (PVD) method. However, at present, the films' application is restricted in some degree because of the lack of study on the relationship between the SWP properties and film formation. Therefore, it is necessary to investigate the plasma properties under the conditions of preparing DLC films. The conventional plasma is excited along the surface of a dielectric material (such as a quartz tube). However, in this paper, we developed a new SWP system—the plasma was excited along a conductive rod (graphite) by microwaves with a frequency of 2.45 GHz. The simple structure, without magnetic fields around the chamber wall, was shown in this paper. The fundamental theories of plasma diagnostic were presented, and plasma properties were studied with a Langmuir probe under the conditions of depositing DLC films by the PVD method. Plasma density, electron temperature, plasma potential and target current were measured at various experimental parameters such as gas pressure, microwave power, and so on. As a result, it was proved that plasma properties are greatly affected by the microwave power, the target voltage and the argon gas pressure in chamber. At the same time, the results indicated that this new system could obtain electron density as high as 10 11–10 12 cm − 3 even at low pressure of 1 Pa.