Cationic Surfactants for the Control of Overfill Bumps in Cu Superfilling

Published

October 10, 2006

Author(s)

Soo K. Kim, Daniel Josell, Thomas P. Moffat

Abstract

Electroanalytical measurements and feature filling experiments have been conducted to study the effect of dodecyltrimethylammonium chloride (DTAC), a quaternary ammonium cationic surfactant, on Cu deposition in the presence of various combinations of superfilling additivies, PEG-CI-SPS. A variety of other surfactants, cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium hydrogen sulfate (CTAHS), and sodium dodecyl sulfate (SDS) were examined to reveal the significance of the head group charge, counter ion, and chain length for the adsorption and interactions of levelers with bis(3-sulfopropyl) disulfide (SPS), the accelerator. A DTAC saturated surface yields substantial inhibition of the Cu deposition reaction that is similar in magnitude to that provided by PEG=C1. This suggests that such layers operate by physically limiting access of Cu_{2+) to the underlying Cu surface. However, the addition of DTAC and related cationic surfactants to the superfilling electrolyte leads to quenching of the characteristic voltammetric hysteresis associated with the PEG-CI-SPS system. This behavior is attributed to ion-pair complex formation between the cationic ammonium head group of the surfactant and anionic sulfonate tail group of SOPS that results in deactivation of SPS. Deactivation may occur either by DTAC accumulation from the electrolyte or by lateral interaction during area reduction that occurs on advancing concave surfaces in accordance with the curvature enhanced adsorbate mechanism (CEAC). The combined process may be optimized to enable the bottom-up feature filling dynamic to be sustained while overfill bump formation is effectively attenuated.

Citation

Journal of the Electrochemical Society

Pub Type

Journals

Keywords

copper, electrodeposition, leveling, superfill

Citation

Kim, S. , Josell, D. and Moffat, T. (2006), Cationic Surfactants for the Control of Overfill Bumps in Cu Superfilling, Journal of the Electrochemical Society (Accessed April 26, 2024)