On temperature and flux dependence of isotropic silicon etching in inductively coupled SF6 plasma

Silicon etching in fluorine-containing plasma has numerous applications due to its high etch rate and smooth profile surface in both anisotropic and isotropic modes. The fluorine source gas significantly affects etching characteristics. Sulfur hexafluoride ( SF6 ) plasma has an order of magnitude higher etch rate in comparison to other fluorine sources and it is mainly used in deep etching processes, such as cryogenic etching. Meanwhile, fundamental reactions underlying this process are still an active research subject. There is only minimal data on the surface reaction probability and most of the existing data is limited to a single plasma condition and sample temperature. In this work, a series of isotropic etching experiments under varying fluorine densities and sample temperatures are performed. In parallel, plasma diagnostics techniques, such as Langmuir probe, optical emission spectrometry, and actinometry, are employed and key plasma parameters deduced. Etching profiles are analyzed, and etch rate and reaction probability values for each etch condition are calculated. The fluorine flux dependence of reaction probability is explained with a kinetic model and model parameters are obtained via curve fitting. No significant temperature dependence of silicon etching parameters is observed. • SF 6 plasma etching of silicon has many applications, still not completely understood. • Etch rate shows no temperature dependence under conditions relevant for applications. • Reaction probability decreases at high F fluxes leading to etch rate saturation. • Our experiments show that cooler chucks lower gas temperature near samples. • Direct estimations of kinetic parameters obtained, allowing more precise simulations.