Development of high-density RF plasma and application to PVD

Development of high density RF plasma sources at low pressures is described based on the production of inductively-coupled plasmas (ICP) for the application to varieties of physical vapor deposition (PVD) processes. Two types of plasma sources are studied; one is an ICP with a conventional helical antenna for magnetron sputtering assistance and the other is a large-diameter ICP sustained with a low inductance double half-loop antenna. In both systems the RF antenna is located within the vacuum chamber and is terminated to the grounded earth potential via a blocking capacitor. By a simple circuit analysis it was found that the floating antenna configuration effectively suppressed the anomalous rise of the plasma potential, which has been verified experimentally. A large-diameter ICP production with a double half-loop antenna of 320 mm in diameter was successfully employed for reducing the antenna inductance, and full coverage of the antenna with an insulator tubing exhibited a significant effect on the suppression of the electrostatic coupling. Azimuthal distribution of the plasma density in this source showed a non-uniformity with m=2 mode. Dense plasmas with plasma density ranging 1011–1012 cm−3 were sustained in both sources. These types of plasmas are expected to be applicable as a tool for enhanced ionization in the sputtering process and for three-dimensional ion based PVD processes.