Defect tolerance in nanodevice-based programmable interconnects: Utilization beyond avoidance

This work focuses on defect tolerance for nanodevice-based programmable interconnects of FPGAs. First, we show that the stuck-closed defects of nanodevices have a much higher impact than the stuck-open defects. Instead of simply avoiding the stuck-closed defects, we use them by treating them as shorting constraints in the routing. We develop a scalable algorithm to perform timing-driven routing under these extra constraints. We also enhance the placement algorithm to recover logic blocks which become virtually unusable due to shorted pins. Simulation results show that at the up-to-date level of nanodevice defects (10⁸-10¹¹x higher than CMOS), compared to the simple avoidance method, our approach reduces the degradation of resource usage by 87%, improves the routability by 37%, and reduce the degradation of circuit performance by 36%, at a negligible overhead of tool runtime.