Microstructural analysis and design of electroplated-Cu micropillar under different process variables and pattern structures

Abstract

Cu micropillars, designed to meet the fine pitch demands of high-performance high-density semiconductor devices, offer superior thermal dissipation and electromigration resistance compared to conventional solder bumps. In microelectronic packaging, the Cu micropillar bump pitch and diameter are adjusted as needed; however, achieving a uniform height across all micropillars for reliable signal transmission remains a major challenge. In this study, the morphology of Cu micropillars electrodeposited in pores was patterned for various structures under different deposition conditions. The micropillar morphological characteristics were measured via scanning electron microscopy, revealing tendencies in micropillar height with respect to the deposition conditions and micropore structure. COMSOL-Multiphysics, a finite-element-analysis-based simulation software, was used to verify the ion concentrations and electrolyte distributions in the structure according to the deposition conditions and micropore structure. The methodology and findings of this study could be used to predict, control, and design the microstructural thickness deviations in processes requiring precise micro-plating structures.