A Modified Bosch Process of SF6/C4F8/O2 ICP-RIE Si Etching

The Bosch process, a widely used ICP-RIE technique, offers several advantages, including uniform etching and high perpendicularity of the etched structure. Nevertheless, due to the unique cyclic process steps inherent to the Bosch process and the isotropy of the etching within a single cycle, the formation of scalloped folds on the sidewalls is almost inevitable and the process is susceptible to defects such as poor perpendicularity of the sidewalls. To overcome these inherent defects, based on the standard Bosch process, we present a new comprehensive SF6/C4F8/O2 etching process. This process exhibits superior anisotropy compared to the conventional Bosch process and is capable of effectively reducing etching defects. Correspondingly, based on the analysis of the chemical etching and physical bombardment in the process, we propose a new F* group dominated etching mechanism. The etching parameters are then optimized according to this new mechanism, resulting in high-quality etching with a positively tapered morphology and nearly vertical smooth sidewalls.