Convection-dependent adsorption and growth modulation mechanism of a novel alkyne additive for high-quality cobalt superfilling

Novel additives are essential for achieving high-quality Co superfilling to advance interconnect technologies. In this work, 3-ethynyl aniline hydrochloride (3-EA), featuring an unsaturated carbon bond and a benzene ring, is used as an effective additive to enable Co superfilling. Electrochemical tests demonstrate that 3-EA exhibits a strong suppressing effect on Co electrodeposition, accompanied by notable convection-dependent adsorption (CDA) behavior. The incorporation of 3-EA significantly improves the surface quality of the electroplated Co layer, reducing roughness and promoting a preferential growth orientation along the HCP (1 0 1). The chemical composition analysis confirms that the electroplated Co layer consists predominantly of nearly pure metallic Co. Theoretical calculations further reveal that 3-EA molecules adsorb on Co crystal planes in a parallel orientation, with CC bond and benzene ring serving as primary adsorption sites, therefore providing a strong suppressing effect. By adding only 10 ppm 3-EA, bottom-up Co superfilling is successfully achieved in different sizes of microvias, and a filling mechanism is proposed to illustrate the bottom-up growth process. These findings show that 3-EA is an effective additive for achieving high-quality Co electrodeposition, offering the potential for application in advanced Co interconnects.