CF4, also designated Freon 14, conforms a methane molecule where all 4 hydrogene atoms have been replaced by fluorine atoms.
Tetrafluormethane is an important process gas for plasma processes, most essentially for plasma etching. While CF4 in principle is a completely inert gas, free fluorine atoms, CF2- and CF3-radicals can be generated by plasma generation. Those are very effective active species especially for etching SiO2. A mix of CF4 and O2 is 5 times more effective for plasma etching than pure Oxygene.