High-speed High-density Cost-effective Cu-filled Through-Glass-Via Channel for Heterogeneous Chip Integration

A topside Cu-filled through-glass via ("Cu bridge") is presented as a novel transmission channel. The simulated signal transmission loss of the Cu bridge was as low as í0.04 dB at a signal frequency of 18 GHz, corresponding to the PCI Express 5.0 bus standard. Its signal transmission loss was less than 0.13 % in a typical long-reach SerDes channel with a loss of í30 dB. The minimum pitch of the Cu bridge was as narrow as 100 μm, which meets the requirements for increased signal I/O. The simple few-step fabrication of the Cu bridge effectively reduces the cost of manufacturing glass interposers. This is a great advantage compared to silicon interposers, which require a complicated process to fabricate Cu through-silicon vias. A glass substrate embedded with Cu bridges supports semi-additive and damascene-based redistribution layers, which increases the number of potential packaging configurations. This Cu bridge is thus a promising approach to next-generation heterogeneous integration based on 2.nD interposers.