DC and Pulsed Boron Plasma and Ion Beam Generation by Planar Magnetron Discharge

Plasma containing boron ions, as well as boron ion beams, are widely used in processes of surface modification and ion implantation¹. In the current work, boron plasma and ion beam were generated using DC and pulsed planar magnetron discharge with pure boron target. The discharge was realized using gradual self-heating of the target by the discharge power. With the target heated by the dc power up to the temperature of more than 300 °C which provides a sufficient electrical conductivity of the target, application of high current discharge pulses becomes possible. The delay time of high-current pulsed discharge current onset can be reduced in order of magnitude down to a few microseconds with background low-current DC discharge. Plasma ion composition was measured by forming the ion beam from the plasma with accelerating voltage up to 20 kV and its subsequent analysis with a time-of-flight methodic². Boron ion fraction reduces during a pulse, which occurs because of the gas desorption from the electrodes, leading to a temporal pressure rise. In turn, pulse repetition rate increase slightly elevates the boron ion fraction. Applying the background DC discharge with current of a few tens of mA reduces a content of unwanted residual gas ions in the pulsed discharge plasma by at least an order of magnitude, as well as increases the boron ion fraction to a value much more than a half. The rest ions are of working gas - argon. Special features of the planar magnetron discharge with hot boron target operation, and boron plasma and ion beam generation are discussed.