Robust and in-situ self-testing technique for monitoring device aging effects in pipeline circuits

Runtime monitoring of aging effects in pipeline circuits is the key to dynamic reliability management techniques which can maximize the performance and energy-efficiency under a reliability envelope without imposing worst-case margin. The existing monitoring techniques are, however, severely limited: for sensor-based techniques, monitoring accuracy is significantly compromised due to the mismatches in aging conditions between sensors and the target circuits, as well as random variation of aging effects; for in-situ techniques, measurement results are sensitive to environmental variations during test phases, also severely reducing monitoring accuracy. We propose a new technique that enables accurate in-situ aging monitoring even under large environmental variations by (i) scaling the supply voltage for temperature-insensitive delay and (ii) reconfiguring target paths into ring oscillators, whose oscillation periods are measured and compared to pre-aging measurement to estimate aging-induced delay degradations. With additional accuracy-improving strategies, the technique achieves highly-accurate monitoring with an error of 15.5% across the temperature variations in self-test phases from 0°C to 80°C, exhibiting >30× improvement in accuracy as compared to the conventional technique operating at nominal supply voltage.