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 fluorine-to-carbon ratio (F/C) of about 0.5 occurs at all incident energies for CF+ ions. This layer grows on top of a mixed amorphous SixCyFz interfacial layer whose thickness increases with E-i. In the case of CF2+ bombardment, the steady-state transitions from relatively slow net fluorocarbon deposition at E-i=50eV to relatively slow apparent net Si etching at E-i=200eV. For 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 interfacial layer whose thickness again increases with E-i, though not as sensitively as in the case of CF+. These findings support the important conclusion that the transition from net deposition to net etching due to fluorocarbon ion bombardment of Si is intimately related tb the amount of energetic fluorine available due to ion fragmentation, which increases with both F content in the ion and ion energy.