Generation of electron-beam produced plasmas and applications to surface modification

NRL has developed a number of hollow cathodes to generate sheets of electrons culminating in a 'Large Area Plasma Processing System' (LAPPS) based on the, electron-beam ionization process. Beam ionization is fairly independent of gas composition and produces low temperature plasma electrons (<0.5 eV in molecular gases) in high densities (10(9)-10(12) cm(-3)). The present system consists of a pulsed planar plasma distribution generated by a magnetically collimated sheet of 2 kV electrons (<1 mA/cm(2)) injected into a neutral background of processing gases (oxygen, nitrogen, sulfur hexafluoride, argon). Operating pressures range from 2-13 Pa with 150-165 Gauss magnetic fields for a highly localized plasma density of similar to10(11) cm(-3). This plasma source demonstrated anisotropic removal rates of polymeric (photoresist) material and silicon with 0, and Ar/O-2/SF6 mixtures, respectively In pure nitrogen, this same source showed a surface nitriding rate of similar to1 mum/h of plasma exposure time on austenitic stainless steel at 400 T. Time-resolved in situ plasma diagnostics (Langmuir probes and mass spectrometry) of these pulsed plasmas are also shown to illustrate the general plasma characteristics. (C) 2003 Elsevier B.V. All rights reserved.