Optimized test circuits for SER characterization of a manufacturing process

Abstract

Novel test circuits for the accurate determination of soft error rate (SER) dependency on critical charges Q/sub CRIT/ have been developed. The minimum charge necessary for flipping the state of a sensor cell, denoted by Q/sub CRIT/, is measured with 1%-2% accuracy before exposing the circuits to radiation. During the accelerated testing, circuits biased with multiple different supply voltages V/sub CC/ are simultaneously placed into a beam and any bit flips are logged. From the measured SER dependency on V/sub CC/ and previously measured Q/sub CRIT/ dependency on V/sub CC/, the dependency of SER on Q/sub CRIT/ can be deduced by correlating V/sub CC/'s for the two measurements. Furthermore, the sensor cell utilizes a single dynamic node which can be programmed to detect strikes on either N- or P-type diffusions, but not both at the same time. The measured dependency SER(Q/sub CRIT/), normalized by the diffusion area, can be used for predicting SER of any other circuit fabricated in the same process and aid designers in optimization for reduced SER. Predictions of a theoretical SER model, if one is available, can be compared directly with the measurements. Since the true Q/sub CRIT/ of the test circuits is known accurately, any discrepancy larger than given by the measurement uncertainty of SER(Q/sub CRIT/) would be clearly due to limitations of the SER model. We implemented the test circuits in a 0.6-/spl mu/m bulk CMOS process and verified accuracy of Q/sub CRIT/(V/sub CC/) calibration method.