A novel radical control method using a radical injection technique was proposed for preventing global warming. This system consists of a new fluorocarbon radical source where-the polytetrafluoroethylene was ablated by a CO2 laser resulting in producing fluorocarbon radicals working as etching species and a radical filter set in front of the radical source which controls radicals generated from the radical source. Therefore, this system does not employ any fluorocarbon feed gases causing the global warming. The system was successfully applied to SiO2 over Si selective etching process employing an electron cyclotron resonance plasma. CFx (x = 1-3) radical densities, F atom densities and higher species were successfully controlled by using the radical filter, which was confirmed by an infrared diode laser absorption spectroscopy and an actinometric optical emission spectroscopy. From these results, it was found that this technique was applicable to SiO2 over Si selective etching process keeping harmony with the environment, particularly for preventing global warming.