Finite-element simulation models and experimental verification for through-silicon-via etching: Bosch process and single-step etching

Abstract

In this study, time-dependent simulation models are established for both the Bosch process and single-step through-silicon-via (TSV) etching using SF6 and C4F8 chemistry by employing a finite-element-method method. The simulation models take into account the thermal etching of F radicals, ion-enhanced etching, neutral deposition and ion-enhanced deposition mechanisms, as well as the angular dependence of the ion sputtering with aspect to a surface element. Comparison between the simulation results and experiments suggests that consideration of two ion fluxes (high-energy and low-energy) is critical for matching the simulation etch profile with the experiments. It is found that the underlying reason for the transition formed on the TSVs using the single-step etching originates from the difference of the ion angular distributions of etching species and depositing species. The Bosch process model successfully predicted profile details, such as the top scallops of the TSV profile, and the model established for single-step etching can be used to predict the transition position shown on the sidewalls. The simulation models can be used to study the individual effects of low-energy ions and the high-energy ions in the etching and passivation mechanisms for TSV etching in both Bosch process and single-step etching techniques.