The species that are desorbed from fluorocarbon films by Ar+ ion bombardment were measured. In this study, we constructed a new apparatus in order to investigate desorption species from fluorocarbon films. The measured fluorocarbon films were deposited on a Si wafer by exposing it to a C2F, plasma in an inductively coupled plasma reactor. The film characteristics were evaluated with x-ray photoelectron spectroscopy (XPS). The C(1s) peak measured in the deposited fluorocarbon films consisted of large chemically shifted peaks produced by C-F-3 and C-F-2 bonds as well as C-CF, bonds. The species desorbed by Arf ion beam bombardment at 1 and 3 keV on the films were detected using a quadrupole mass spectrometer (QMS). The ratios among CF, CF2, CF3, and CF4 species, which were measured with the appearance energies by QMS, indicate that CF4 is a dominant desorption species with the ratio of 80% among them at the beginning of bombardment at 3 keV and 65% at 1 keV. As the ion dose increased, the total amount of desorption species was reduced. XPS measurement indicated that the ion bombardment changed the characteristics of the fluorocarbon films from F-rich to C-rich. This implies that the species desorbed from fluorocarbon films during etching changed gradually.