Stabilization of Ar plasma by applying longitudinal magnetic field

This research is intended to obtain a stable plasma with a low gas pressure by applying a magnetic field parallel to the gas flow in the discharge region of a double-tubed coaxial line-type microwave plasma CVD system so that the diffusion of the plasma in the radial direction is suppressed. The stability of the plasma is studied by the width of variation and temporal change of the electron saturation current, hi the case where the Ar gas flow rate is 30, 20, and 15 ml/min, the stability of the plasma is good. Improved stability is seen on application of a magnetic field. Also, in the case of Ar gas flow rate of 10 and 8 ml/min, the plasma is unstable without a magnetic field. By applying a magnetic field of more than about 500 gauss, the diffusion of electrons to the discharge tube wall is suppressed and as a result the extinction of electrons at the wall is reduced. Hence, a stable microwave plasma is obtained even at a low gas pressure (low gas flow).