3-D Thin film interposer based on TGV (Through Glass Vias): An alternative to Si-interposer

Interposers for SiP will become more and more important for advanced electronic systems. But through substrate vias are essential for the 3-D integration. Being a standard for laminate based materials this is much more complex for Si-wafers: High speed etching has to be combined with complex electrical isolation, diffusion barriers and void-free Cu-filling. Without doubt this can be solved in lab-scale but for high production scale cost is a tremendous barrier. Glass wafers with W-plugs have been intensively investigated in this paper. A new acronym has been posted to high-light this technology: TGV for Through Glass Vias. The results of modeling and simulation of TGV at RF/Microwave frequencies showed a very good compromise between wafer thickness, TGV-shape and via diameter for vertical metal plugs with 100 µm diameters in 500 µm thick glass wafer still very stable for thin film wafer processing without costly temporary wafer bonding processes. Therefore the HermeS^® from Schott was chosen as the basis for a prototype of a bidirectional 4 × 10 Gbps electro-optical transceiver module. Thin film RDL and bumping of these wafers was possible without any modifications to Si-wafer. First thermal cycles showed very promising results for the reliability of this concept.