The results of an experimental study on the development and testing of a plasma reactor for controlled atomic-layer etching of ultrathin material layers using low-energy argon ion beams are presented. The ion beams are generated using a ribbon-like electron beam produced by a pulsed periodic discharge with a long hollow cathode and a mesh anode at gas pressures of 0.05–0.5 Torr and pulse voltages with amplitudes of up to 1.5 kV. The cathode is a cylindrical stainless-steel rod 25 mm in length and 12 mm in diameter, containing a rectangular cavity (slot) 3, 4, or 5 mm wide and 6 mm deep. A nichrome mesh anode is positioned 6 mm from the cathode; the mesh size is 25 × 25 μm, the wire thickness is 25 μm, and the geometric transparency is approximately 70%. The electron beam is accelerated by a voltage applied to an electrode located 1 mm from the mesh anode and is then transported over a distance of 15 mm to a collector, where it forms a plasma sheet with an area of 15 × 25 mm2. This plasma sheet acts as a wide-aperture ion source that bombards the substrate surface. The ion flux plasma source consists of the extended hollow cathode, an electrode system that forms the plasma sheet, and a system for directing the ion flux onto the substrate surface. CF2.75 flanges with electrical vacuum feedthroughs were used to supply voltage to the plasma-source electrodes. The uniformity of the plasma sheet was experimentally evaluated as a function of the hollow-cathode characteristics, gas pressure, and collector potential. The hollow cathode is shown to generate a ribbon electron beam with a density of approximately 1012 cm–3 and an electron energy of up to 1.1 keV. The electron and ion densities in the plasma sheet reach maximum values of about 1011 cm–3, while the ion energy near the substrate surface can be controlled in the range of 1–50 eV. A sufficiently uniform plasma sheet is formed at electron beam energies above 1 keV. In addition, a kinetic model of an argon ion plasma source for the reactor geometry under consideration has been developed.
Ashurbekov et al. (Mon,) studied this question.