NEW BROAD-BEAM GAS ION-SOURCE FOR INDUSTRIAL APPLICATION

A source delivering a broad, high current ion beam compatible with bot h chemically active and inert has been developed which gives reliable, long term, maintenance-free operation. It uses a glow discharge with a cold cathode in a magnetic field where a dense uniform plasma is gen erated in large volumes at low gas pressures. Optimal selection of the electrode configuration and magnetic field ensures operation at press ures lower than 0.1 Pa in pulse-periodic mode (1-10 A discharge curren t, 1 ms pulse length, 25-50 Hz frequency), and continuous mode (discha rge current up to 2 A). The current density of a 15-cm-diam beam can r each 10 mA cm(-2) in the former, and 1 mA cm(-2) in the latter. Tests with a 50-cm-diam discharge chamber show the uniformity of the ion emi ssion current to be better than +/-10%, confirming that the technology is scaleable, and that beams of up to 2000 cm(2) cross-sectional area can be obtained without loss of beam uniformity through appropriate d esign of the extraction system. The source is completely reactive gas- compatible, generating ion beams from oxygen, nitrogen, argon or ioniz ed CH radicals (e.g., using C3H8). Mass-charge beam analysis shows the beams, generated to be of high purity (>99%). Applications include lo w energy (1-3 keV) ion beam cleaning of glass, ceramic and metal surfa ces prior to the deposition of protective and decorative coatings such as TiN and diamondlike carbon, ion beam assisted deposition, and high energy gas ion implantation using, e.g., guise-periodic beams of ions with energies up to 50 keV. (C) 1996 American Vacuum Society.