2019 Influence of the Temperature-Dependent Cu+1-Accelerator Complex Formation on Through-Silicon Via Filling

Authors:
Ralf Schmidt, Josef Gaida and Cornelia Jäger

Journal:
ECS, Journal of the Electrochemical Society, 2019, Volume 166, Issue 8, D350-D353, DOI:10.1149/2.2.1251908jes

Institut:
Atotech Deutschland GmbH, R&D Semiconductor, Berlin 10553, Germany

Abstract:
The influence of the temperature-dependent Cu+1-accelerator complex formation on through-silicon via (TSV) filling was studied by means of electrochemical polarization and plating experiments. Electrochemical studies revealed increasing cuprous ion concentration upon addition of the accelerator additive in comparison to the additive-free electrolyte and further increase upon increasing temperature. This indicated formation of a Cu+1-accelerator complex. The electrochemical results were compared to TSV plating experiments at different temperatures. Despite improved mass transport of cupric ions into the high aspect ratio TSV feature at elevated temperatures, large voids were obtained under these conditions, while void-free bottom-up filling was achieved at room temperature. This effect was ascribed to acceleration of the copper deposition in the upper part of the feature due to increasing Cu+1-accelerator complex concentration at higher temperatures. The resulting counter action the effect of the suppressor additive in this part of the features is assumed to yield the observed voids by closure of the features at an early stage of the plating process. Thus, the results presented here reveal the importance of taking into account the comprehensive impact factors on copper deposition for TSV applications and help to improve and fine tune the process to challenging structures.