Very low pressure RF glow discharge plasma using multi-dipole surface magnetic fields

Summary form only given. It is shown that, by taking advantage of surface multidipole fields, RF glow discharges can be maintained down to pressures at least as low as 2×10^-5 torr. Large effective electrode separation and good plasma uniformity can be achieved. Only one conventional electrode was used. Two different types of RF powered electrodes were explored: a conventional plate with a diameter of 1.5 cm and a rod with a diameter of 1.3 cm. The line cusps replace the other electrode. Line cusps fully surround a 20-liter plasma. Experiments employed argon plasmas with 13.56-MHz RF power. A second grounded electrode was also employed. This plate differed from the powered electrode in that it was located within the surface magnetic field. Adjustment of the separation of this plate from the magnet plane permits continuous variation of the maximum surface magnetic field seen by plasma and the effective loss area at the electrode. The plasma potential can be continuously varied by changing the position of the grounded plate and the surface magnetic field is effective in improving plasma confinement at pressures at least as high as 10^-3 torr