The Influences of Iodide Ion on Cu Electrodeposition and TSV Filling

Abstract

Through silicon via (TSV) technology has been researched for 3-dimensional packaging of electronic devices, and Cu electrodeposition has been used for TSV filling. The organic additives are one of the most important factors in Cu electrodeposition affecting Cu gap-filling, and the leveler usually plays a decisive role. In this research, iodide ion (I−) is adopted instead of organic leveler for Cu bottom-up filling. The behaviors of I− are investigated by various types of electrochemical analyses. Especially, the influences of I− on the adsorption of the accelerator and suppressor are extensively studied, and it is confirmed that I− makes the suppression layer robust while reducing the adsorption of the accelerator. Also, it was observed that the effect of I− is greater under the strong convection of electrolytes than without convection, meaning that I− could induce selective deposition at the bottom of the features. Based on this, TSV-scaled trenches are successfully filled by potentiostatic Cu electrodeposition in the presence of the accelerator, suppressor, and I− without any organic levelers.