Nuvotronics will develop a robust wafer-level integration technology using our proprietary PolyStrata interposer to enable high-frequency interconnects and routing between two dis-similar substrates: silicon, SiGe, GaAs, GaN, InP wafers. The PolyStrata passives grown on the wafers will consist of high performance interconnects capable of aligning and soldering the two wafers using copper pillars to create a Ball Grid Array (BGA). Establishing novel wafer-to-wafer push fit technologies will demonstrate sub 5psec interconnection delay between technologies. With integration of low loss routing between the technologies, our proposed interposer can monolithically integrate passives such as high Q inductors, filters, resonators directly between the two wafers. The PS interposer offers an excellent structure to improve the CTE mismatch between wafers and enable thermal heat piping to direct the heat away from the different stack. In Ph I, Nuvotronics will demonstrate the integration of GaAs on Silicon using the PS interposer technology. The goal: to integrate a 1"x1" GaAs and Silicon die, demonstrating interface loss < 0.3dB and sub 5psec interconnection delay. The design will integrate CTE compensation structure to enable over 100C of temperature variation. Nuvotronics will design and optimize the interface between PolyStrata and silicon, and between GaAs and PolyStrata, to minimize stress and improve mm-wave RF performance. Next, Nuvotronics will fabricate a surrogate silicon and surrogate GaAs wafer with PolyStrata interface. A solder ball back-end process will be applied to both wafer technology and integration of solder balls. The 4" wafers will be diced in 1"x1" dies before being integrated. DC and RF measurements will demonstrate electrical performance. Preliminary temp. cycling will be performed to demonstrate reliability of the interface. In Ph II, Nuvotronics will demonstrate 4-inch wafer level integration and performance under temp. cycling.