Extraction of positive and negative ion beams from large area plasma sources

Abstract

In this study we investigate extraction and acceleration of positive and negative ions from a pulsed inductively coupled plasma (ICP) in oxygen and hydrogen. Experiments were performed in a directed ribbon beam system where ions can be produced at an incident angle non-normal to the target. Positive and negative ions were transported to the wafer. The RF plasma source, extraction electrodes and wafer were biased synchronously. The energy of extracted ions closely follows the amplitude of the applied bias voltage and it ranges from few hundreds of volts to 10 kV. The peak beam current density can reach 100 A m−2. The ion beam angles, ion current, and ion composition are reported. The injection physics requires correlating the positive and negative ion and electron densities near the extraction opening with the extracted currents. The plasma was modeled using CRTRS, a plasma fluid code that self-consistently solves for ICP power deposition, electrostatic potential, and plasma dynamics. A new perspective on the possible production of angled ion beams on surfaces is discussed.