DOI 10.1007/s10825-010-0340-9 Impact of RDF and RTS on the performance of SRAM cells

Abstract This paper investigates electrical effects due to reliability phenomena associated with the downscaling of transistors in advanced technologies, particularly Random Telegraph Signal (RTS) and Random Dopant Fluctuations (RDF). RDF and RTS are becoming important issues in sub-60 nm technologies, mainly in memories, where transistor sizes are smaller. This paper presents a comprehensive eval-uation of the impact of the joint effect of RTS and RDF on 6T-SRAM cells. Based on 3-D atomistic simulation of the device structure, doping profile, and trap location, the ran-dom threshold voltage variation caused by the joint effect of RDF and RTS is evaluated. The derived threshold volt-age variation is then used to statistically evaluate the per-formance variation at the circuit level. Finally, the impact of assuming a normal distribution for the threshold voltage variation caused by RDF and RTS is studied. The results ob-tained running Monte Carlo simulations raffling the value of the variation of the threshold voltage from a database ob-tained by 3-D atomistic simulation are compared to the re-sults obtained running Monte Carlo simulations considering the variation of the threshold voltage as a Normal distribu-tion. The results show that for a 6T-SRAM designed with 45 nm technology the read noise margin distributions are very similar between the two cases, making the Normal dis-tribution a good approximation for the Vth variations. Nev-ertheless, the performance variation induced at the circuit level does not necessarily follow a normal distribution