Anomalous vertical twins with high (2 2 0) texture in direct current electroplating copper film

The regulation of crystal structure and orientation during direct current (DC) electrodeposition is one of the key factors for achieving performance control of the electrodeposited copper films. In this paper, we found that during continuous DC electrodeposition in acidic electrolytes containing additives, the electrolyte aging promotes spontaneous transformation of the crystal structure of copper. A special crystal structure, i.e., vertical twins with high aspect ratio exhibiting a high (2 2 0) orientation, was revealed, which is mainly attributed to the minimization of energy in the deposited film. We further pointed out that the generation priority of vertical twins was between the equiaxed structure (UD-type) and the (1 1 1) textured columnar structure (FT-type). The inhibitions resulted from the complex interactions and degradation of additives are the driving forces for crystal transformation. Moreover, the surface roughness changes with the transformation process of the crystal structure, which provide a potential method to regulate the surface roughness of copper film.