Atomic force microscopy examination of Cu electrodeposition in trenches

Electrodeposition of copper in trenches with several acid cupric sulfate electrolytes containing benzotriazole (BTA), 4,5-dithiaoctane-1,8-disulfonic acid (SPS), polyethylene glycol (PEG), or chloride (Cl) has been probed by in situ atomic force microscopy (AFM) and ex situ scanning electron microscopy (SEM). The two techniques provide complementary information. A series of AFM images reveals dynamic morphology changes of deposits and trenches during open-circuit dissolution and electrodeposition. Analysis of these AFM images shows 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. While there is a good correlation between grain size and overpotential observed with AFM, this correlation does not extend to the interior structures observed with SEM. Different additives are found to influence growth with behavior ranging from clear conformal growth with BTA to nascent superfilling with SPS + PEG + Cl^-.