Effects of Organic Additives on Grain Growth in Electrodeposited Cu Thin Film during Self-Annealing

Abstract

The microstructural changes in electrodeposited Cu films during self-annealing is demonstrated in this study. The structural change is strongly influenced by the organic additives in the Cu electrodeposition. The use of either polyethylene glycol (PEG) or bis-(3-sulfopropyl)disulfide (SPS) decreases the Cu(111) grain size of deposited films, as the adsorption of the additives suppresses the surface diffusion of the Cu ions during the electrodeposition. After the electrodeposition, the average grain size of the deposited film was simultaneously increased by 10% in a self-annealing process to reduce the defect energy, which is mainly composed of the surface energy of the grains. Meanwhile, the grain grew 4 times larger than the as-deposited grain size during the self-annealing when both the PEG and SPS were introduced. The drastic grain growth was attributed to the accumulation of a high defect energy in the deposited film. The dynamic interaction between the co-adsorbed PEG and SPS on the Cu surface during the electrodeposition promotes an unoriented dispersion-type deposition, resulting in high-strain energy as well as surface energy. Releasing the strain energy accumulated by the high density of misorientation also leads to the simultaneous growth of Cu(200) grains. (c) 2017 The Electrochemical Society. All rights reserved.