Optimizing the Isotropic Etching Nature and Etch Profile of Si, Ge and Si0.8Ge0.2 by Controlling CF4 Atmosphere With Ar and O2 Additives in ICP

An isotropic etching, etch rate and surface roughness of Si, Ge and Si_0.8Ge_0.2 subjected to CF₄/Ar/O₂ plasma has been studied using inductively coupled plasma (ICP) system. First, we applied the etching parameters on the silicon substrate to observe the etching rate using carbon tetrafluoride (CF₄) under different flow rates and choose the parameters of high etch rate. The chosen parameters for silicon was CF₄ (60 sccm) and etching in different ratios of argon (Ar) and oxygen (O₂) were also discussed. Second, it also reports on selective isotropic etching for germanium (Ge) and Si_0.8Ge_0.2 by ultrahigh vacuum chemical vapor deposition (UHVCVD) and was etched under selected conditions used for silicon under different atmospheres in an inductively coupled plasma system. Starting from a pure CF₄ gas that etches Ge and Si_0.8Ge_0.2 with a good selectivity to silicon, the modification of gas mixture was also investigated. A possible mechanism based on the favored action of CF₄ is investigated. Relative etch rate between Si, Ge and Si_0.8Ge_0.2 are explained with etch rate reductions achieved by selective CF₄ plasma chemistries with Ar/O₂. Etched profile, surface roughness was examined and measured by using SEM and AFM technique.