Existing silicon on insulator (SOI) pixel detectors which integrate single gate transistors with substrate diodes are limited by two key problems. First, the SOI transistor performance is degraded by the large potentials that must be applied to the substrate to fully deplete the diodes. Secondly, the performance of these SOI pixel detectors degrades with exposure to radiation due to charge trapping in the buried oxide. However, SOI pixel detectors offer the best resolution at high speed while using less power at lower cost than competing technologies like monolithic active pixel detectors or 3-D chip stacking. American Semiconductors next generation FlexPix SOI pixel detector technology provides all of the benefits of existing SOI pixel detectors, but eliminates the two key problems that limit performance. FlexPix combines multi-independent gate Flexfet transistors with diode detectors integrated in the substrate. Flexfets unique multi-gate architecture effectively shields the transistor channel and eliminates the performance degradation due to both substrate bias and radiation charge trapping. Feasibility of the next generation x-ray imager has been established by successful completion of the design, layout, simulation, and analysis using the FlexPix SOI pixel detector technology. All Phase I technical objectives were met or exceeded through the collaborative research effort between American Semiconductor and the Fermilab Particle Physics Division. American Semiconductor exceeded the program objections by also completing the design, layout and simulation of two FlexPix advanced characterization test chips that in Phase II will provide key detector data to facilitate future designs by other government and commercial groups and spur business growth in Phase III and beyond. Successful manufacture of the substrate diodes in the FlexPix technology was demonstrated in an earlier Phase I program. Fabrication and testing of two FlexPix wafer lots will enable iterative design and process optimization to meet the requirements of the MAMBO x-ray imaging application and provide detailed process information for future business development. The first manufacturing run will employ the multi-chip configuration completed in Phase I containing both the basic x-ray imager design and the two pixel characterization test chips. The second manufacturing run will allow for design and process optimization based upon testing from the first wafer lot. For the second wafer lot, the team will create a full-scale MAMBO FlexPix x-ray imager prototype that will provide a key demonstration of the technology to spur additional business development in Phase III. Commercial Applications and Other
Benefits: The FlexPix technology will lead to improvements in pixel detectors used in medical, military, government and related commercial imaging applications. Specific applications include high dynamic range biomedical x-ray, nondestructive and non-invasive testing, health physics, and environmental studies.
