Transmission lines and vias on a novel SUbstrate, metallic NAnowire based, for Millimeter-wave Interposer – TSUNAMI

The TSUNAMI project is mainly related to the information, communication and nanotechnologies priority axe of the « Stratégie Nationale de Recherche et d’Information » (SNRI). In particular, this project will develop solutions for future advanced communication systems in the millimeter-wave (mmW) frequencies for applications like high-data rate telecommunications for fast video-streaming (from 57 GHz to 66 GHz in Europe), automotive radars (76 GHz to 81 GHz), RF-imaging (94 GHz, 140 GHz and above). These solutions will be based on a new mmW Metallic-Nanowire-filled Membrane substrate (MnM-substrate), developed using nanotechnologies that will increase the capacity (reduced losses) and the miniaturization of the mmW circuits.

The concept of this MnM-substrate is already undergoing the process for the deposition of two patents that should occur no later than April 2012 through Floralis (valorization subsidiary of the University Joseph Fourier). The first patent is related to the concept of slow wave transmission line using the MnM-substrate. The second patent is related to a new high-performance miniaturized vias on the MnM-substrate as an interposer. Further, Floralis will manage a valorization process of the TSUNAMI outcomes to an integrated devices and 3D integration manufacturer..
The MnM substrate consists in a dielectric alumina membrane with a moderate density (20-40%) of parallel, vertical, good conductor nanowires. A thin low-loss dielectric layer covers the top of the membrane. The transmission line is a classical microstrip transmission line deposited on the top of the oxide cap layer whereas its ground plane, on the opposite side of the substrate, contacts the nanowires. Such configuration easily provides a slow-wave effect in high frequency transmission lines.

Moreover, state-of-the-art through-package-vias (TPVs) used for 3D integration present complex and expensive fabrication and require large diameter to reduce losses at mmW frequencies. On this MnM-substrate, TPVs are low-cost and of very simple fabrication since the metallic nanowires cross the entire substrate allowing connection between both sides. Further, as the signal in the MnM-via is transmitted through several nanowires instead of a solid metal, losses and size are reduced.

The two academic partners of this consortium with the help of the valorization subsidiary Floralis, complement each other perfectly with all the required know-how for achieving this project’s goal. Related to the realization of the interposer, the complementarities between the Nanosciences Department of the Institut Néel, which enjoys of an exceptional environment to fabricate adequate, accurate, high performance nanostructured membranes, and the UJF-IMEP-LAHC, which is very famous now for its slow-wave transmission lines based devices design, fabrication and characterization is crucial for the success of this project. Floralis’ integration to the consortium, as a subsidiary of UJF-IMEP-LAHC is the link to industry. Floralis's key objective is to transfer technology emanating from UJF laboratories to the market through a variety of relevant, targeted business models (business unit, proof of concept, licensing …).

STMicroelectronics, Crolles, France, is very interested by the results that will be carried out in the TSUNAMI project, as shown by the support letter added in the Appendix of the project. STMicroelectronics is attracted by the low-cost, high-efficiency and high-flexibility of the new membrane that will be developed in this project.

The requested funding is very reasonable, and proves that the technology carried out to fabricate the membranes and the devices that will be designed is really low-cost.