A Novel Scheme for Wide Bandwidth Chip-to-Chip Communications

Quilt Packaging (QP), a novel chip-to-chip communication paradigm for system-in-package integration, is presented. By forming protruding metal nodules along the edges of the chips and interconnecting integrated circuits (ICs) through them, QP offers an approach to ameliorate the I/O speed bottleneck. A fabrication process that includes deep reactive ion etching, electroplating, and chemical-mechanical polishing is demonstrated. As a low-temperature process, it can be easily integrated into a standard IC fabrication process. Three-dimensional electromagnetic simulations of coplanar waveguide QP structures have been performed, and geometries intended to improve impedance matching at the interface between the on-chip interconnects and the chip-to-chip nodule structures were evaluated. Test chips with 100 μm wide nodules were fabricated on silicon substrates, and s-parameters of chip-to-chip interconnects were measured. The insertion loss of the chip-to-chip interconnects was as low as 0.2 dB at 40 GHz. Simulations of 20 μm wide QP structures suggest that the bandwidth of the inter-chip nodules is expected to be above 200 GHz.