Synthesis and application of a TEG-based leveler and its derivatives on Cu electrodeposition

Abstract

Through-Silicon Via (TSV) is a vertical electrical interconnection passing through a silicon wafer or IC chip, and it provides the shortest interconnects between multiple chips. Although the smallest pad size can be achieved with TSV technology, the defect-free filling of TSV remains as a challenge for successful chip performance. To afford the defect-free filling, the bottom-up filling is required, and some organic additives are essential elements during the electrodeposition of Cu. Among the additives, a leveler has been known as a convection dependent adsorbent, which means it selectively adsorbs on the opening of feature and inhibits Cu-electrodeposition. In this thesis, the structure-activity relation of a leveler, a key element for defect-free filling, has been studied with newly synthesized levelers. The triethylene glycol based leveler (Lev (1)), having simple linear center chain with ammonium functional groups at the end of the backbone, has been designed to closely investigate the properties of the levelers. Starting from ethylene glycol, epoxide rings have been introduced at the both ends after allylation. To introduce ammonium groups, the epoxide rings have been opened with N,N-dimethyl amine, and following methylation successfully produces Lev (1) in 46% of overall yields. To find out the effect of the center chain, the Lev (1) was modified to levelers (Lev (2), (3), (4)) having various center chain. The levelers have been synthesized in 25~50% of overall yields. The electrochemical analyses of the levelers with linear sweep volatammetry (LSV) confirmed that the all synthesized levelers showed the desired convection dependent adsorption behavior and the longer, and aliphatic center structure showed stronger adsorption on the Cu surface. The levelers also afforded successful gap filling performance in the presence of an accelerator and a suppressor.