A Study on Glass Surface Activation Process to Enhance Glass-Metal Adhesion Strength in Glass Advanced Packaging

Due to its excellent characteristics (high-modulus, low losstangent, CTE match), glass substrates have great market potential to replace, or eliminate silicon interposers to achieve high-density, high-bandwidth, and low-power glass advanced packaging systems. However, the poor adhesion strength between glass and metal is one of the major technical bottlenecks of glass packaging, resulting in glass-metal delamination. This paper focuses on the study of glass surface activation mechanism to improve glass surface hydrophilicity, and thus to increase the adhesion strength between glass surface and seed layer. The adhesion strength between glass and seed layer was characterized by cross-hatch peel adhesion test and cantilever beam tensile test. The results show strong adhesion between glass surface and sputtered Cu/Ti-Cu seed layer. The adhesion strength reaches the highest 5B adhesion level, and is larger than 4.9 N/cm according to the cross-hatch peel adhesion test. The cantilever beam tensile test also shows that the adhesion is strong enough so that glass cracks first before seed layer de-laminates. Finally, ~12 μm thick Cu was electroplated, followed by dual-beam focused ion beam (DB-FIB) characterization. The DB-FIB images show that no de-lamination occurred among plated Cu, Ti-Cu seed layer and glass surface.