Fragmentational collisions in reactive ion beam processing

Abstract In a reactive ion beam etching (RIBE) system ion beams extracted from source plasmas by a two-grid optic with energies below 500 eV were analysed by energy selective quadrupole mass spectrometry (QMS). Both non-reactive plasmas (Ar) as well as reactive source plasmas with O 2 , SF 6 and CF 4 as feed gases were investigated at typical working pressures of 10 −2 -10 −1 Pa (10 −4 -10 −3 mbar) in the process chamber. At these conditions gas phase collisions of the ions with the background gas particles are likely to occur between the source and the substrate usually positioned at a distance of 20–30 cm from the grids during a process. For the generation of reactive and molecular ions, respectively, an ECR plasma source was used. From the energy distributions a strong indication of dissociative collisions in the process chamber was found as a significant phenomenon for a wide range of ionic species. Our results may be compared with mass and energy selective etch/deposition studies to discuss some aspects of gas phase fragmentation for the resulting surface properties.