Novel Process Of SiO/sub 2//Si Selective Etching Using New Gas System Against Global Warning

1 .Introduction In SiOn/Si selective etching plasmas, fluorocarbon gases are usually employed. The fluorocarbon gases, however, cause serious environmental problems, namely global warning. The production of fluorocarbon gases will be prohibited in the near future. Therefore, development of novel processes using alternative feed gases for avoiding the environmental problems. In this study, we have developed a novel process of SiO2/Si selective etching on the basis of a new idea of radical injection, which enabled us not to use any fluorocarbon gases at all and to control radicals precisely. In this new system of radical injection, polytetrafluoroethylene (PTFE) is ablated by a CO2 laser and species generated by the laser ablation are injected into the etching apparatus. This system has not only great advantage of no use of fluorocarbon gases but also the small capacity of gas feed stock, simplicity of gas flow system and safety. The characteristics of CFx(x=l-3) radical densities and the other molecules with plasma and without plasma were measured by infrared diode laser absorption spectroscopy (IRLAS) and mass spectroscopy. Moreover, SiO2/Si etching using ECR plasma with this new radical feed system was performed.