Plasma dry desmear of Ajinomoto build-up film for fine micro-via fabrication in advanced semiconductor packaging

Abstract

The increasing demand for high-performance computing and AI applications has accelerated the development of advanced semiconductor packaging technologies with high I/O density. Ajinomoto build-up film (ABF) is widely used as a dielectric material in redistribution layers (RDLs) due to its low dielectric constant and low thermal expansion coefficient. However, laser drilling of ABF generates residual smear composed of silica and polymeric resin, which deteriorates copper adhesion and signal reliability in micro-via structures. In this study, a plasma-based dry desmear process using CF4/O2/Ar gases was investigated to effectively remove smear while minimizing via hole expansion. The desmear behavior was systematically analyzed as a function of via size and plasma gas composition using CCP-RIE equipment. Energy-dispersive X-ray spectroscopy (EDS) analysis identified Si-containing residues at the via bottom. The addition of Ar enhanced physical sputtering and improved smear removal efficiency. Focused ion beam–scanning electron microscopy analysis showed that the optimized dry desmear process effectively removed smear residues while suppressing hole expansion. Compared with the conventional wet desmear process, the plasma dry desmear achieved approximately 2 μm less hole expansion, which is critical for fine-pitch micro-via fabrication. These results demonstrate that plasma-assisted dry desmear provides a promising approach for next-generation high-density advanced packaging technologies.