Adhesion and reliability of direct Cu metallization of through-package vias in glass interposers

Direct metallization of bare glass with copper is required to reach the full potential low-cost benefit of glass interposers. However, this poses a fundamental materials challenge associated with copper-to-glass adhesion. Intermediate polymer liners on glass have been used by others, adding an extra material and processing step. In this paper, three approaches to direct metallization of copper to glass interposers are explored and reported. Electroless plating, sputtering followed by electrolytic plating, and sol-gel were investigated as Cu deposition methods with an emphasis on adhesion and reliability of copper to bare glass. The adhesion and reliability performance of films were characterized by tape-testing, peel-strength measurements, and thermal-shock testing. Based on these results, individual assessments are made for each approach and compared with others to assess future directions.