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Significance statement
An thorough finite-element simulation model has been established to predict the through silicon via (TSV) etch profiles produced by both Bosch process and single-step etching. The model established in this study has included the ion-assisted etching and polymer deposition mechanisms by considering the interactions of various etching species.
The advantages of this molecular flow model include: (1) The effect of high-energy and low-energy ion species can be individually studied in the model as simulation parameters. (2) A time-dependent parameter ramping mechanism has been included in the simulation model for multi-step etching processes (for example, the Bosch process). (3) Ion-enhanced polymer sputtering and deposition are considered as an integral of all incident ion fluxes arriving at any surface orientation by considering their angular dependence.
With these advantages, the simulation of the Bosch process is realized by integrating the etching and passivation model in an alternating manner. And the simulation of the single-step etching process is modeled considering the dissociation paths and interactions of major etching species. In the simulation model, the etch rate realized by the experimental profile has been paired with the ion and neutral fluxes. The predicted effect of the pressure, bias voltage, gas flow rate computed by the simulation model all agrees well with the experimental profiles. More importantly, some detailed profile feature observed from the experimental profiles, such as sidewall scallops and aspect-ratio dependent etching (ARDE), has been successfully observed in the simulation results. The comparison between the TSV etch profiles simulated using the model established in this study and experimental profiles shows that this simulation model can successfully predict both the etch rate and morphology of the TSV profiles etched by a Bosch process and single-step process.
Vac. Sci. Technol. A32, 041303(2014); Zihao Ouyang1, Wenyu Xu1, D. N. Ruzic1, Mark Kiehlbauch2, Alex Schrinsky2 and Kevin Torek2
- Center for Plasma Material Interactions, Department of Nuclear Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 and
- Micron Technology, Inc., 8000 South Federal Way, Boise, Idaho 83707.
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 ofetching 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.
