| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 100 === Copper electrodeposition has received interests in recent years because it is an important process to fabricate interconnects in modern semiconductor architecture. Thiol molecules are common organic additives in copper plating solution, as they when coupled with chloride ions activate Cu deposition. This act of activation is presumed to facilitate superfilling or bottom-up filling of Cu deposit. By contrast, exposed areas on a silicon wafer are shown to be largely deactivated by the blocking act of polyethylene glycol (PEG).
Self-assembled monolayer (SAM) is effective in changing characteristics of surfaces. In this study, the spatial arrangements and coverages of SAMs of mercaptoacetic acid (MAA) and 3-Mercapto-1-propanesulfonate sodium (MPS) adsorbed on Au(111) electrode have been characterized by scanning tunneling microscope (STM) and cyclic voltammetry (CV) in 0.1 sulfuric acids. Voltammetry was used study the stability of these thiol molecules on the Au(111) electrode as a function of potential; meanwhile, molecular-resolution STM imaging was used to explore the organization of these molecules as a function of time and electrode potential. with their –COOH and –SO3 terminal groups, these thiol molecules could interact strongly with copper cations. Voltammetric results show that copper cations were more strongly clung to –COOH. STM imaging was not able to identify adsorbed copper cations on the electrode surface.
PEGs with molecular weights of 4000-8000 were used to study the suppressing effect of these molecules on Cu deposition. STM results show that Cu deposit grew in layers and 3D in 0.1 M H2SO4 with and without PEGs. The rate of Cu deposition was evidently fast. The presence of MAA and MPS in the electroplating bath evidently blocked and facilitated Cu deposition. These results are closely relevant to the deposition of Cu in recessed features, as MPS was able to induce superfilling; whereas MAA failed to implement superfilling.
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