Accelerator Surface Phase Associated with Superconformal Cu Electrodeposition

Published

March 5, 2010

Author(s)

Thomas P. Moffat, Liang Yueh Ou Yang

Abstract

Superconformal film growth is a key process in state-of-the-art Cu metallization of electronic devices. Superfilling of recessed surface features results from competition between electrolyte additives that accelerate or inhibit Cu electroplating. In situ STM is used to image the accelerating SPS-Cl- surfactant phase that is responsible for displacing and preventing formation of the inhibiting PEG-Cl- layer. Various aspects of competitive and/or co-adsorption of Cl- and SPS on Cu(100) were examined for industrially relevant additive concentrations. At potentials associated with superfilling, a saturated, c(2x2) Cl- ordered adlayer forms on the surface. When SPS is added individual molecules are imaged as a mobile 2-D gas diffusing on the Cl- adlattice. The SPS-Cl- surfactant accounts for many aspects of additive function previously observed and stipulated by the curvature enhanced accelerator model of superconformal film growth. Several SPS derived species of differing mobility and tunneling contrast appear with exposure time. The lattice gas species are sensitive to the imaging conditions with tip-molecule interactions particularly evident at higher tunneling currents. At negative potentials the c(2x2) Cl- adlayer is disrupted by an order-disorder transition, while desorption occurs at more negative potentials. This allows SPS direct access to the Cu metal whereupon irreversible sulfide formation occurs.

Citation

Journal of the Electrochemical Society

Pub Type

Journals

Keywords

Cu, Damascene Processing, In Situ STM, Superconformal Film Growth, SPS, TSV

Citation

Moffat, T. and , L. (2010), Accelerator Surface Phase Associated with Superconformal Cu Electrodeposition, Journal of the Electrochemical Society (Accessed February 22, 2026)