Tin dioxide thin films doped with fluorine were prepared by using a radio-frequency (RF) magnetron sputtering method. The target was SnO2, powder mixed with either SnF2 or SnF4 powder. The deposition conditions for obtaining films of low resistivity and their physical characteristics were systematically studied. The crystallinity, which was inferior to that of the CVD prepared film, was not improved by increasing substrate temperature, decreasing total pressure, and decreasing RF power. These changes in deposition conditions decreased the fluorine content of the film and consequently decreased carrier concentration.