Morphology of films deposited on the sidewall during the Bosch process using C4F8 plasmas

In the Bosch process, C4F8 plasmas are used to deposit passivation films. In this study, the passivation films were deposited in micro-scale trenches by changing the C4F8 flow rate, ICP power, and pressure, and their cross sections were observed by scanning electron microscopy. The results showed that the morphology of the passivation film and its relative deposition rate at each depth varied depending on the plasma discharge conditions. There is a correlation between the C–CF x bond content and the morphology of passivation films, with high C–CF x bond content resulting in smooth morphology and low C–CF x bond content resulting in a rough morphology. Furthermore, it was found that ion bombardment reduced the roughness of the passivation film. Through these experiments, we also found the possibility of controlling the deposition rate of the passivation film at each trench depth by adjusting the plasma discharge conditions.