Hydrofluorocarbon ion density of argon- or krypton-diluted CH2F2 plasmas: generation of CH2F+ and CHF2+ by dissociative-ionization in charge exchange collisions
Abstract
Ion densities of CH2F+ and CHF2+ were determined by dissociative ionization pathways in channels of charge exchange collisions, i.e. CH2F2 + M+ → CH2F+ + F + M* and CHF2+ + H +M* [M = Ar, Kr] in CH2F2 plasmas diluted by a rare gas [M]. These channels simultaneously generated counter fragments of charge-neutral H and F atoms of interest for plasma etching processes. In Ar-diluted plasmas, CH2F+ ions predominated due to dissociative ionization between Ar+ [ca. 15.8 eV] and C-F appearance [dissociative ionization] energy [ca. 16 eV] to form CH2F+. In contrast, for Kr-diluted plasmas, C-H appearance energy [ca. 13.8 eV] predominated to produce a larger amount of CHF2+ ions due to a similar channel for charge exchange collisions between Kr+ [ca. 14 eV] and CH2F2. Thus, adding the ratio of Ar and Kr gas to CH2F2 plasmas provided control over the fraction of CH2F+ and CHF2+ ion densities.
- Publication:
-
Journal of Physics D Applied Physics
- Pub Date:
- February 2015
- DOI:
- 10.1088/0022-3727/48/4/045202
- Bibcode:
- 2015JPhD...48d5202K