Development of a high density glass interposer based on wafer level packaging technologies

Currently glass is mainly used as unstructured wafers or panels with the highest market share in glass capping applications. Higher functionality in glass is driven by the applications in RF and Photonics. Since the technologies of via interconnects in Si and glass are completely different, it is challenging to perform a direct and fair comparison. Mainly laser technology and electrical discharge are used for forming the vias into the glass. Slightly modified thin film technologies already in mass production in WLP can be used to fill the vias with a copper metallization. Conformal metallization and full via plating are options. High yield and excellent reliability have been achieved. Generally, due to the lossy nature of silicon and complex polarization mechanism that occurs at the Si-SiO2, TSVs may suffer from severe signal integrity and EMI problems such as huge insertion loss, delay and cross-talk, depending on the Si-resistivity considered. Therefore, regarding the dielectric material, TGVs have significant advantages over TSV, especially when either LRS or MRS is used. In summary TGVs show excellent RF characteristics over TSVs. This has been proven for a test design up to 40 GHz.