CHARACTERIZATION OF A SLOT ANTENNA MICROWAVE PLASMA SOURCE FOR HYDROGEN PLASMA CLEANING

A new large volume microwave plasma source has been used for the production of a hydrogen; plasma. The source consists of an annular waveguide cavity with axial slots on the inner side which acts as a field applicator to sustain a plasma at 2.45 GHz. The plasma is contained in a fused silica bell jar of 16 cm in diameter and 20 cm in height. The distance between the slots corresponds to a waveguide wavelength. The source is able to generate a highly dissociated (up to 90%) hydrogen plasma for cleaning purposes. Stable operation of the plasma source is shown for a pressure range of 0.1-1.3 mbar and a power range of 600-2000 W. The plasma can be ignited over the entire examined pressure range, and the power needed for discharge ignition is below 1.7 kW. The minimum ignition power is 1050 W for a pressure of 0.7 mbar. A double Langmuir probe and optical emission spectroscopy were used to characterize the hydrogen plasma as a function of microwave power, pressure, and position. The results indicated a typical ion density of 1.5X10(11) cm(-3) which is an order of magnitude less than that obtained for argon under similar conditions. The typical electron temperature is 2.5 eV for microwave power of 2 kW and pressure of 0.7 mbar. (C) 1995 American Vacuum Society.