Study of glass metallization and adhesion evaluation for TGV application

The density of the packaging is recently increasing for miniaturization of the electronic system, especially 3D SiP (System in Package). Interposer is a significant research area for 3D packaging which always uses three kinds of materials including silicon, glass and organic. Currently, there are a lot of researches about silicon interposer because the CTE (Coefficient Thermal Expansion) and process is match with semiconductor process. But, from the index of each material, glass interposer is very promising for electronic packaging. Glass interposer has chemical stability, low material cost, high isolation property and low relative dielectric constant. Moreover, the CTE of glass is range value that can be a buffer between IC and substrate. The coefficient of thermal expansion of glass is more similar to silicon's, compared to the organic materials. One of key technology of developing glass interposer for TGV application is metallization especially adhesion layer which can have a good adhesion with glass. This paper presents the adhesion of metallization layer on Pyrex glass. Several metal thin films such as Ti, TiW, Cr, were separately deposited on glass wafer by sputtering process. Scratch test has performed to evaluate adhesion strength of thin film on glass wafer. Effects of metal type, thickness and glass roughness on adhesion strength are studied. Environmental reliability tests are also performed to confirm evolution of the adhesion layer strength during thermal shock experiments. Finally, by a series of experiments a better material as adhesion layer have been found, the relationship between the surface roughness, thickness and adhesion performance have been figured out and the thermal shock aging profile would be found.