This Small Business Innovation Research Phase I project will develop a hybrid substrate based, Si-on-SiC, for application to X-band circuitry. This innovative approach incorporates the advantages of compound semiconductor devices with the incumbent advantages of Si processing and circuit technology to form hybrid circuits which will enable advanced high-frequency (X-band) amplification systems. The hybrid circuits will be made using a highly-thermally conductive hybrid substrate, so that the heat generated in the X-band devices will be efficiently carried away from the active area. This unique hybrid substrate is a Si-on-SiC hybrid wafer comprised of a very thin Si membrane (~1 micron) that has been sliced from a Si wafer and attached to a SiC wafer. Incorporating an X-band device in close proximity with Si signal processing electronics reduces signal noise compared to the tradional approach of completely seperated systems, while the SiC of the hybrid wafer wicks heat away from both the X-band and Si electronics, thereby allowing for increased power-density of devices, increased packing density of devices per unit area, or some combination of the two. Furthermore, electronics fabricated in the Si layer of the hybrid wafer have all of the advantages of SOI electronics: the ability to operate at high temperatures, resistance to parasitic currents and radiation hardness.
The general hybrid circuit technology being developed could also be applied to power conversion systems or any application where SOI based electronics are subjected to high power and high temperature levels. Approximately 2.5 million 200 mm diameter equivalent SOI wafers were produced worldwide in the year 2004 alone. The hybrid wafers offer superior thermal performance compared to conventional SOI while maintaining the incumbent advantages of SOI over bulk Si. This project will lead to improved X-band radar systems for military applications. A typical airborne x-band radar antenna consists of one to three thousand transmit/receive(T/R) modules, each with its own high frequency GaAs amplifier producing on the order of 10 W of power. This makes heat management a critical issue. Overall system size is also an important issue for military applications. Given that a radar system will perform better with more T/R modules, the need to minimize T/R module size is paramount. This project addresses possible solutions to both heat management and T/R module size reduction.
