Abstract

This thesis encompasses studies of copper electrodeposition and copper oxide formation. In situ atomic force microscopy (AFM), ex situ scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and electrochemical measurements were employed in order to interrogate the growth, inner microstructure, and composition of electrodeposits obtained from various additives containing solutions. The deposition with benzotriazole (BTA) containing solutions yields smooth deposits while additive-free deposition gives the roughest deposits. Several systemically modified benzotriazole (BTA) compounds were used to explore the growth mechanism of electrodeposits with BTA containing solutions. The images and the scaling analysis clearly show a marked effect of triazole ring substitution on the copper deposition. The different action exerted by these compounds can be explained by their ability to form oligomers with cuprous ions. Significant inclusion of organic matter and sulfur species was found in the deposits obtained from additive solutions by SIMS measurements.

The electrodeposits obtained from electroplating baths containing 4,5-dithiaoctane-1,8-disulphonic acid (SPS), polyethylene glycol (PEG), Cl⁻, and several SPS derivatives were examined to investigate the synergic effects of these additives. SIMS results show that SPS is always included into Cu electrodeposits, while PEG is never included. Cl⁻ is included into deposits only when SPS is present. SIMS and overpotential measurements with several SPS derivatives suggest that S_thiol of SPS makes SPS bind to Cu and included into the deposits. Sulfonate groups of SPS drive proper solvation of SPS in acid solution with copper sulfate. Decomposition of SPS and the chain length of SPS are not critical to alter the characteristics of the accelerators.

In situ AFM was employed to observe a dynamic filling behavior in trenches during electrodeposition. The analysis of AFM images provided insight into the vertical and lateral growth of deposits in addition to cross sectional profile evolution. The grain size analysis obtained from AFM images has been correlated with structures observed in cross sectional SEM images.

Voltammetry and potential-dependent forces between a Si₃N ₄ cantilever and a Cu(111) surface were used to probe the oxidation and reduction of this material in basic solution. The results showed the potential-dependent formation of insoluble and soluble copper oxide species at or near Cu(111) surface.