Effect of Basicity of Amino Group at Side Chain in Diallylamine-Type Copolymer Additive on Via-Filling by Copper Electrodeposition

Abstract

In a previous study, we achieved the bottom-up via-filling during copper electrodeposition using a single diallylamine-type copolymer additive instead of the conventional four types of additives. However, we have not yet established the relation between the function of this single additive and the polymer structure. To investigate the additive function and the strength of the polymer additive's basicity, we synthesized a series of diallylamine-type copolymers having two amino groups on the polymer side chain, added them to a basic acid copper sulfate bath as a single additive, performed the electrodeposition, and observed the via cross sections using an optical microscope (OM). We also performed an electrochemical analysis based on quartz crystal microbalance (QCM) and linear sweep voltammetry (LSV) measurements. By comparing the amino group at the end of the side chain with the one near the main chain, it was found that the basicity of the latter is weak due to the neighboring group effect. However, when the distance between these two amino groups is long, the basicity of the amino group near the main chain is strong. The use of a polymer additive with a strong amino group near the main chain had the effect of suppressing the electrodeposition outside the via and achieving a good bottom-up filling.