Numerical Study of SF6/O2 Plasma Discharge for Etching Applications

SF6/O2 plasma discharge has extensive applications in semi-conductor industry for anisotropic etching of silicon. Herein, a self-consistent fluid model has been used to investigate the capacitive coupled SF6/O2 plasma discharge. A complete set of reactions in gas phase which include electron impact reactions, ion-ion reactions, neutral–neutral reactions and charge transfer reactions in tandem with the primary processes such as dissociation excitation, and ionization were incorporated in the model. The densities of dominant plasma species (both neutral and charged) were calculated. Furthermore, the impact of O2 concentration on the plasma characteristics was studied. The results showed a bell shape distribution for neutral species while uniform distribution for charged species at center of the discharge. Moreover, it was demonstrated that the dominant etching species in the discharge were F, O, S, SF5+, FO, F+, O+, O2+ and S+. With the increase of O2 concentration in the plasma, there is a decrease in the ratio of neutral species (i.e., F/ O) and overall etch rate, signifying that chemical etching is the prominent process for the discharge. In conclusion, the anisotropic etching of Si substrate can be efficiently achieved using the optimum input parameters for SF6/O2plasma discharge.