Mechanism of Microtrench Generation in Etching of Wiring Trench on SiO2 Layer

In this study, we reveal the effects of various factors that influence microtrench generation using a high-precision simulation model of etching of wiring trench on a SiO2 layer. It is considered that the behaviors of ions and fluorine that contribute to etching, as well as the CO/C4F8 + CO flow rate ratio, have an effect on the microtrench generation. The number of ions on the trench bottom that contributes to the etching rate is larger at the side edges than at the center. This indicates that the trench bottom becomes a microtrench profile. Otherwise, the number of fluorine absorbed and used for etching is larger at the center of the trench bottom than at the side edges, regardless of the incident angle of radicals. This indicates that the trench bottom becomes a round profile. Moreover, an increase in CO/C4F8 + CO flow rate ratio decreases the number of fluorine at the side edges compared with that at the center. This indicates that the trench bottom becomes a more round profile. These simulation results reveal the mechanism of microtrench generation in the wiring trench of a SiO2 layer. Furthermore, we clarify guidelines for setting the conditions of the microtrench-free etching of a 200 nm trench bottom on a SiO2 layer.