Plasma immersion ion implantation based on glow discharge with electrostatic confinement of electrons

A new approach to plasma immersion ion implantation (PIII) is presented featuring glow discharge with electrostatic confinement of electrons being used for plasma generation. Its obvious advantage is a comparatively low cost price of related equipment capable to establish at gas pressures of 10−5–10−2 mbar in the working chamber volume of several liters up to dozens cubic meters dense and homogeneous plasma. Any vacuum chamber made of conductive material may be used as an electrostatic trap for plasma electrons and a DC power supply is well enough to maintain the discharge. Theoretical and experimental results reveal dependence of stationary glow discharge on electron losses and reduction of anode-to-chamber voltage under the influence of energetic electrons emitted from the surface of negatively biased substrate. Plasma density growth rate depends on amplitudes of high voltage pulses applied to the substrate and to the plasma. Two variants of PIII-systems are described. In the first system plasma ‘on duty’ is established with stationary discharge and negative high voltage pulses applied to the substrate, give rise to high current pulses in its circuit. In the second system two high voltage pulses of equal amplitude are being simultaneously applied to the substrate (negative pulse) and to the plasma (positive pulse). Energy of electrons bombarding the chamber walls and the anode of the second system is two times lower than the energy of singly charged ions bombarding the substrate. Practically, the second system ensures 1 order of magnitude reduction of X-ray yield, thus improving the safety.