Plasma enhanced surface treatments using electron beam-generated plasmas

NRL has developed a ‘large area plasma processing system’ (LAPPS) utilizing a high energy (∼2 keV) modulated electron beam to drive the plasma ionization. This system has been shown to be (1) efficient at producing plasma in any gas composition, (2) capable of producing low temperature plasma electrons (<0.5 eV) in high densities (109–1012 cm−3) and (3) scalable to large area (square meters). In this work, the progress of a number of applications using LAPPS is discussed. Nitride growth in stainless steel was investigated, which demonstrated high rates (up to 20 μm/h1/2) at low temperatures (≤462 °C). Complementary mass spectrometry showed that the nitriding results correlated to the flux of atomic ions delivered to the substrate. LAPPS was also combined with magnetron sputtering sources to form hybrid systems for surface pretreatments of polymers for metallization and thin film deposition of nitrides. In these systems, Teflon® substrates pretreated with an oxygen LAPPS exposure demonstrated a significant increase in copper and aluminum film adhesion compared to untreated substrates, with the dominant factor believed to be the changed surface morphology. The simultaneous operation of LAPPS with a titanium magnetron sputter source increased the growth of the 〈200〉 orientation in TiN films, due to the increased atomic nitrogen ion flux. Additional LAPPS systems are also discussed.