Heterogeneous Integration Enabled by 3-D Stitch-Chips

A fully customizable interconnect technology for radio frequency (RF) heterogeneous integration (HI) applications is proposed and demonstrated in this article. The 3-D stitch-chip (3DSC) consists of two components: a pitch-transitioning coplanar waveguide housed on a fused-silica substrate, and a through-silicon via chiplet that functions as a vertical signal transmission path. A test vehicle consisting of a fused-silica board and a silicon chip was created, whose components were subsequently interconnected with the 3DSC. A baseline was established with a separate test vehicle that was interconnected with wire-bonds. Measurement in the Ka-band across the full signal chain between the $200~\mu $ m-pitch chip and the $300~\mu $ m-pitch board resulted in >16 dB return loss and <1.3 dB insertion loss. The electrical optimization process of the constituent components and full signal-chain is detailed. The fabrication method is provided and its results are discussed.