Design of a Non-contact Vertical Transi- Tion for a 3d Mm-wave Multi-chip Module Based on Shielded Membrane Supported In- Terconnects

The preliminary design concept, for a low-loss, highbandwidth electromagnetically coupled vertical transition for use as a via between adjacent levels of a 3D-MCM based on membranesupported striplines with micro-machined shielding, is presented. The design methodology, modeling using Ansoft HFSS and simulated results are presented and together represent a complete electrical characterization of the vertical transition. The simulated insertion loss of these structures is shown to be as low as 0.12 dB at 60 GHz with a 44 GHz 1 dB bandwidth. Besides studying the vertical transition, the analysis is extended to identify the range of directional coupling which can be achieved using this type of structure, which is shown to be greater than 3 dB. The structures studied rely on a versatile micromachining technique for the fabrication of the micro-shielding which allows for the conformal packaging of lines and devices, with the ultimate aim of realizing 3D system-in-a-package type modules. The concept and proposed fabrication techniques for these modules, including methods of flip-chip MMIC attachment are detailed.