Atomistic simulation of fluorocarbon deposition on Si by continuous bombardment with energetic CF+ and CF2+

We have conducted molecular dynamics simulations of continuous CF+ and CF2 ion bombardment of Si with incident energies E-i of 50, 100, and 200 eV at normal incidence. Continuous deposition of a fluorocarbon layer with a flu orine-to-carbon ratio (F/C) of about 0.5 occurs at all incident energies fo r CF+ ions. This layer grows on top of a mixed amorphous SixCyFz interfacia l layer whose thickness increases with E-i. In the case of CF2+ bombardment , the steady-state transitions from relatively slow net fluorocarbon deposi tion at E-i=50eV to relatively slow apparent net Si etching at E-i=200eV. F or CF2+, at all E-i's, a relatively thin carbon-rich fluorocarbon overlayer with a F/C ratio of 0.5 also forms on top of a more fluorine-rich mixed in terfacial layer whose thickness again increases with E-i, though not as sen sitively as in the case of CF+. These findings support the important conclu sion that the transition from net deposition to net etching due to fluoroca rbon ion bombardment of Si is intimately related tb the amount of energetic fluorine available due to ion fragmentation, which increases with both F c ontent in the ion and ion energy. (C) 2001 American Vacuum Society. [DOI: 1 0.1116/1.1322652].